15 Medical Virology (142)

Question 1

An unknown virus has been isolated in the laboratory from mouse epithelial cells, which contain reverse transcriptase. The genetic material from this virus is examined and found to contain adenine, guanine, cytosine, and uracil, but no thymine. What can be concluded about it?

1 It is a retrovirus
2 It is a DNA virus
3 It is a prion particle
4 It cannot undergo integration
5 It can only infect bacteria

Answer 1

It is a retrovirus

A retrovirus contains RNA as its genetic material, and uses the enzyme reverse transcriptase to convert its single stranded RNA genome into a DNA/RNA helix which is then converted to a DNA duplex. This then inserts into the host chromosome, is replicated, and eventually gives rise to single stranded RNA to be incorporated into the new viral particle. RNA and DNA have three bases in common (adenine, guanine, and cytosine) but RNA contains uracil and DNA contains thymine as the fourth base. Therefore, finding uracil in the viral genome indicates that it is an RNA containing virus. Since it contains reverse transcriptase, we can deduce that it is retrovirus.
Prion is a type of infectious agent that lacks nucleic acid, and is made up only of protein. Prion is a short form for proteinaceous infectious particle.
The process of incorporating the genetic material of a virus into the host genome is known as integration. Retroviruses can undergo integration. Bacteriophages (and not retroviruses) infect bacteria only.

Question 2

A 28-year-old male presents to the office with bilateral cervical lymphadenopathy of 2 cm with mild fever and sore throat for 1 week. He also complains of nausea and decreased appetite. On examination, there is hepatosplenomegaly and palatal petechiae. A new intern diagnoses him with streptococcal throat infection and prescribes antibiotics. The patient comes back the next day with a painless, itchy rash all over his body. The antibiotic that was most likely given to this patient is

1 Benzathine penicillin
2 Erythromycin
3 Amoxicillin
4 Cephalexin
5 Clindamycin

Answer 2

Amoxicillin

The patient probably has infectious mononucleosis (IM), which was diagnosed wrongly and treated with Amoxicillin. Amoxicillin causes a non- allergic rash in patients having infectious mononucleosis. The underlying pathomechanisms are still unknown. The clinical decision to use antibiotics in acute pharyngitis is complicated by the identical presentation of both viral and bacterial illnesses. If empiric therapy is elected, the incidence of hypersensitivity reaction is less common with penicillin or tetracycline compared to ampicillin or its analog, amoxicillin.
Infectious mononucleosis, caused by Epstein-Barr virus (EBV), is a disorder that typically occurs in young adults and it is characterized by fever, sore throat, headache, malaise, nausea, and anorexia. Lymphadenopathy is usually present and splenomegaly may be observed. In the early phases of the infection, T lymphocytes become activated and they restrain viral replication in B-lymphocytes. The lymphocytosis characteristic of this period consists primarily of T lymphocytes with cytotoxic phenotype (CD8+). A humoral response is also present during acute IM and is characterized by non-EBV-specific response such as the production of Heterophil antibodies. Treatment is usually bed rest and steroids are indicated for impending or established airway obstruction.
The viral rash is faint, usually non-pruritic, and fades away rapidly. The drug-induced rash is pruritic and lasts for a longer duration than the typical viral rash seen in IM.
Benzathine penicillin interferes with synthesis of cell wall mucopeptides during active multiplication, which results in bactericidal activity. It is given for the prophylaxis of streptococcal throat infection. It does not cause a rash in IM.
Erythromycin inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. It is used in the treatment of Strep throat, but it does not cause a rash in IM.
Cephalexin is a first-generation cephalosporin that arrests bacterial growth by inhibiting bacterial cell wall synthesis. Primary activity is against skin flora and it is used for skin infections or prophylaxis in minor procedures. Orally, cephalosporins are effective in the treatment of streptococcal pharyngitis, but they do not cause a rash in IM.
Clindamycin is a lincosamide used for treatment of serious skin and soft tissue staphylococcal infections. It is also effective against aerobic and anaerobic streptococci (except enterococci). It inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. It does not cause a rash if given in IM.

Question 3

Case
Over a period of 1 month, 42 persons from the local community, mostly adults, were seen in an ophthalmic clinic situated in one of the East Asian countries. Most of them had attended the clinic for other ocular problems a few days preceding the onset of symptoms.
The presenting symptoms were soreness and redness of eyes, photophobia, foreign body sensation, and excessive tearing. Some complained of ocular and periorbital pain and decreased visual acuity. Duration of the illness varied from 3-14 days. On examination, swelling and erythema of the eyelid, conjunctival hyperemia, chemosis, and follicular reaction mainly of the lower conjunctiva were seen in all patients. Superficial punctate keratitis and discrete sub-epithelial opacities were observed in those who complained of decreased visual acuity. An outbreak of keratoconjunctivitis (epidemic keratoconjunctivitis) in the community was suspected. Conjunctival swabs cultured on Hep2 cells showed cytopathic effect (CPE), characterized by marked rounding, enlargement, and aggregation of affected cells into grape-like clusters. Human adenovirus group antigen was detected in the infected tissue culture cells by immunofluorescence using antihexon antibody. Investigation of the source of infection revealed presence of adenovirus on the tonometer tip.

Certain types of adenoviruses are known to be commonly associated with particular disease manifestations.

Of the adenovirus types listed below which is most likely to be responsible for this outbreak of keratoconjunctivitis?

1 Type 37
2 Type 34
3 Type 40
4 Type 12
5 Type 7

Answer 3

Type 37

Type 37 is one of the 3 adenovirus types commonly associated with Epidemic Keratoconjunctivitis (EKC). The others are types 8 and 19 and all 3 types belong to subgroup D adenoviruses. Adenovirus type 8 was initially identified and considered as the most important causative agent of EKC. More recently, types 19 and 37 have been recognized as causative agents of this highly contagious disease. Type 37 is reported to have caused 3 large epidemics of EKC in northern Japan.
EKC is a serious disease as it involves both conjunctiva and cornea. In most cases, the infection remains self-limited. Acute phase involving viral replication lasts up to 2 weeks. Often the acute phase is followed by immune T-cell mediated infiltration of the corneal stroma leading to the formation of multiple sub epithelial infiltrates. These infiltrates can cause disturbances in vision, which may last for months. EKC outbreaks have been reported in eye clinics, hospitals, nursing homes, camps, and military bases. Major mode of transmission is through hands, ophthalmic instruments, and ophthalmic solutions.
Adenoviruses are extremely hardy when deposited on environmental surfaces. Adequate disinfection of ophthalmic instruments and hand hygiene are important in preventing transmission.
Adenoviruses are non-enveloped double stranded DNA viruses, 70-90 nm in size with a characteristic morphology. The viral capsid is composed of 252 capsomeres arranged as an icosahedron with 20 triangular facets and 12 vertices. The capsomeres consist of pentons and hexons. Pentons occur at the 12 vertices and the rest are hexon capsomeres. Penton consists of penton base and protrusion of fibers with a rod-like portion and a knob at the distal end. Thus the virion has the appearance of a space vehicle. Hexons, pentons, and fibers constitute the major antigens of adenoviruses. All human adenoviruses share a common hexon antigen and can be detected by complement fixation, immunofluorescence, or ELISA. Another group reactive antigen is present in penton base. The penton base carries toxin-like activity and causes cytopathogenic effect (CPE). The fibers contain type-specific antigens and are important in typing. The virus attaches to cells by the fibers. Hemagglutinating activity of adenoviruses depends on fibers.
Human adenoviruses are classified into 6 subgroups (subgenera) A-F based on their biologic, immunologic, and biochemical properties (hemagglutination, fiber length, DNA fragment analysis, and oncogenic potential). The groups differ in their ability to agglutinate rat and monkey RBCs and this property of hemagglutination is useful for identifying the subgroups.
Neutralization and hemagglutination inhibition tests are used for typing isolates. Different genome types also have been identified.
Adenoviral infection is species specific. Of the 51 human adenovirus types identified, more than one type may produce the same clinical syndrome and one type of virus may cause different diseases. The virus replicates only in cells of epithelial origin and shows the property of latency. In the infected cell the virus replicates in the nucleus and produces large intra nuclear inclusions.
Though cultural isolation and identification of the virus is important from epidemiological point of view, it is time consuming. Detection of adenoviral antigen in conjunctival cells by direct immunofluorescent assay (DFA) is rapid and found useful.
Molecular methods based on polymerase chain reaction (PCR) have been recently developed for the detection of adenovirus DNA in conjunctival swabs. A multiplex PCR-enzyme hybridization assay is reported to be of use for detecting all adenovirus species (A through F) simultaneously in a single test. This test is found to be rapid, specific, and sensitive.
For the diagnosis of adenoviral infections, detection of specific antibodies in the serum is helpful. Rise in titer of antibodies should be demonstrated in paired sera. Complement fixation or ELISA can be used for detecting antibodies against group antigen. Neutralization test detects type specific antibodies.
Type 34 and type 35 are associated with infections following transplantation and belong to group B adenoviruses. Patients may develop fatal disseminated infections especially following bone-marrow transplants. Post transplant adenovirus infections are more common in pediatric patients. Infection may be often endogenous caused by the reactivation of latent adenovirus or can be exogenous.
Type 40 and type 41 are known as enteric type adenoviruses. These viruses are associated with diarrhea occurring in infants and belong to group F adenovirus. Both these types are fastidious and fail to grow on conventional tissue cultures used for growing adenoviruses. The viruses are present in abundance in diarrheal stools and can be demonstrated by electron microscopy. Enzyme Immuno Assay (EIA) and latex agglutination (LA) commercial kits are available for detection of enteric adenoviruses in stools.
Type 12 belongs to group A adenoviruses and experimentally proved to be one of the most strongly oncogenic type. Inoculation of types 12, 18, and 31 into baby hamsters induces tumors. So far there is no evidence relating adenoviruses and natural malignancy in humans or animals.
Type 7 is a group B adenovirus commonly associated with several clinical syndromes. The diseases include pharyngitis, pharyngoconjunctival fever, acute respiratory disease (ARD), and pneumonia in infants and immunocompromised hosts. ARD outbreaks caused mostly by types 4 and 7 and occasionally by type 3 have been reported in military recruits. In the United States, a vaccine against types 4 and 7 was being used for military personnel for several years and was discontinued in 1990.
Adenovirus types 3 and 7 produce follicular conjunctivitis which is milder, usually occurring as a manifestation of pharyngoconjunctival fever. This is also known as swimming pool conjunctivitis. Outbreaks may occur, often associated with children’s summer camps. Similar ocular manifestations may be caused by Chlamydia trachomatis.
No licensed systemic or topical antiviral drug is available for treatment of adenoviral infections.

Question 4

Case
A 45-year-old woman residing in US was seen at the medical clinic for sudden onset of fever, shivering, headache, bilateral conjunctivitis, retroorbital pain, and acute pain in her limbs and joints. She had traveled to India 4 weeks ago and returned 3 days ago after spending her vacation. She became ill soon after returning to the US. While she was in India, there was an ongoing epidemic of an arboviral infection in the country. The virus responsible for the epidemic belonged to genus Alphavirus (Togaviridae family) and was transmitted by Aedes aegypti mosquitoes.
After physical exam and routine laboratory investigations, clinical diagnosis was “viral fever”. The patient was placed on symptomatic treatment with analgesics and anti-inflammatory drugs. She became afebrile on the 7th day after onset of her illness and all symptoms except the joint pains resolved within 14 days. As the arthralgia persisted even after 2 months, she had to seek medical advice. Based on the possibility of travel-associated infection, serological tests were done. The test results came positive for specific IgM antibodies and neutralizing antibodies against the arbovirus that was causing the extensive epidemic in India.

What is the most likely viral agent that caused illness in this patient?

1 Sindbis virus
2 West Nile virus
3 Yellow fever virus
4 Chikungunya virus
5 Dengue virus

Answer 4

Chikungunya virus

Chikungunya virus is a mosquito-borne arbovirus and belongs to genus alphavirus of Togaviridae family. In Asian countries, the vector is Aedes aegypti mosquitoes. During 2005-2006, an epidemic of Chikungunya occurred in India and >1.4 million cases were reported in 2006. This epidemic was caused by an African genotype of the virus. In US, travel-associated chikungunya has been reported in returning travelers from India and SW Indian Ocean Islands where the outbreak originated. Though the symptoms of the patient are characteristic of Chikungunya, other viral fevers may clinically resemble this disease.
All other viruses listed are arboviruses transmitted by mosquitoes; they can be excluded due to the following reasons:
West Nile, Yellow fever, and Dengue viruses are not alphaviruses. They belong to genus flavivirus of Flaviviridae family. Sindbis is an alphavirus and has not been reported to have caused epidemics in India. The main vector for this species is Culex mosquitoes.
Alphaviruses are spherical viruses 70 nm in diameter with single-stranded positive-sense RNA genome. The neucleocapsid is wrapped inside a lipid layer upon which the envelope proteins are displayed. Envelope proteins mediate binding to host cells and the virus particles enter the cytoplasm of the host cell by endocytosis. Virus replication occurs in the cytoplasm. Viral assembly takes place at the host cell surface and the viruses acquire their envelope from the plasma membrane through budding. Most of the alphaviruses possess hemagglutinating ability.
Chikungunya virus causes endemic and epidemic infections indigenous to tropical Africa and Asia. The disease is characterized by acute onset of fever, arthralgia and sometimes arthritis. Related arthralgia and arthritis may persist for months. Conjunctivitis and maculopapular rash are other manifestations that may appear. In travelers returning from areas affected by an ongoing epidemic, Chikungunya infection is considered as a probable diagnosis if they develop these symptoms. An extensive epidemic has been reported from the Reunion Islands. Aedes albopectus was the vector. Imported cases have been reported from US. Indigenous transmission is possible as the vector mosquitoes belonging to Aedes species are present in the country. In the urban areas, the viral infection is maintained by a man-mosquito cycle. No animal reservoirs have been identified in the urban cycle. A sylvatic cycle similar to that of Yellow fever involving wild primates and forest dwelling Aedes species of mosquitoes has also been observed.
Vertical maternal-fetal transmission of the viral infection has been reported. Chikungunya viral genome was detected in the amniotic fluid, placenta, and brain tissue of the infected fetus.
Laboratory diagnosis depends on isolation of the virus in cell cultures, reverse-transcription polymerase chain reaction (RT-PCR) based assays for detection of the viral genome, and serological test for antibodies. Virus specific IgM can be demonstrated by enzyme-linked immunosorbent assay (IgM-capture ELISA) and neutralizing antibodies can be detected by plaque reduction test. For diagnosis during the first week of illness, PCR is more reliable than serology.
There is no specific treatment or vaccine available. Infection results in life-long immunity.
Sindbis virus is the prototype alphavirus. It causes Sindbis fever. Virus is maintained in nature by transmission between vertebrate hosts and mosquito vectors, mainly Culex mosquitoes. Sindbis fever is characterized by sudden onset of fever, myalgia, arthralgia, and rash. The disease is found in Asia, Africa, the Middle East, and Europe. Many species of birds and mammals have been identified as reservoir hosts. Experimental studies have shown that Sindbis virus has specific cytotoxicity for cancer cells. It causes necrosis of cervical tumors in mice. It is suggested that a specific strain of Sindbis virus (SIN AR339strain) could be a promising agent for human cervical and ovarian cancer therapy.
West Nile, Yellow fever, and Dengue viruses belong to the Flavivurus genus. Flaviviruses replicate in the cytoplasm of the host cell. The particle assembly takes place in intracellular vesicles. They are 40-60 nm in diameter and possess single-stranded positive sense RNA genome.
West Nile virus is transmitted by Culex species of mosquitoes. Generally birds are found as natural reservoirs. Infection may be subclinical or may cause acute mild febrile disease with lymphadenopathy and rash. The virus may cause fatal encephalitis in aged persons. An epidemic of West Nile virus infection with several cases of meningoencephalitis occurred in the US in 2002. Person to person transmission by organ transplantation, blood transfusion and breast feeding have also been reported.
Yellow fever virus is the prototype member of Flaviviridae family. Yellow fever is an acute febrile illness found only in Africa and Central and South Americas. In severe cases, liver and kidneys are affected and jaundice, proteinuria, and hemorrhagic manifestations are seen. Urban yellow fever is transmitted by Aedes aegypti mosquitoes. Jungle yellow fever is a disease of monkeys and the sylvatic cycle involving monkeys and wild mosquitoes maintain the virus in nature. 17D vaccine is a very effective, attenuated virus vaccine against yellow fever. It is the most effective preventive measure.
Dengue virus causes dengue fever. The virus is of worldwide distribution predominantly in tropical region. The disease is characterized by fever, myalgia, joint pains, lymphadenopathy, and rash. Dengue hemorrhagic fever and dengue shock syndrome are severe forms of the disease. Vector is primarily Aedes aegypti. Aedes albopectus is also known to transmit dengue. Epidemics have been reported from several countries including India.

Question 5

Case
Within 48 hours of consumption of raw oysters from a restaurant in North Carolina, 3 men in their 30s developed diarrhea and severe vomiting accompanied by headache, low-grade fever, and chills. They recovered with administration of intravenous fluid. In a week’s time, all other adults and children in their households became sick with similar symptoms. Bacterial causes were excluded in the laboratory. A viral agent was considered as the cause of this outbreak of gastroenteritis.

What is a likely characteristic of this virus?

1 Enveloped virus, 70-80 nm size
2 Genome contains double-stranded RNA
3 Replicates in the nucleus of the host cell
4 Cultivable in vitro on HEp2 cells
5 Can survive temperature as high as 60°C
6 Only a single genotype has been identified

Answer 5

Can survive temperature as high as 60°C

The viral agent responsible for the outbreak of gastroenteritis is most likely to be a norovirus. Norovirus (a group of Norwalk-like viruses) is the cause of >90% of non-bacterial gastroenteritis in the U.S. and is the most important cause of viral gastroenteritis involving adults. Food-borne outbreaks are common. Uncooked or inadequately cooked shellfish is one of the important sources. Other viruses of gastroenteritis (Group A rotavirus, sapovirus, astrovirus, adenovirus types 40 and 41) are mostly associated with infections in children less than 5 years old. Norovirus can survive at temperatures as high as 60°C and up to 10ppm chlorine. The virus does not possess the other characteristics listed.
Norovirus genus belongs to the family Caliciviridae. The virus is non-enveloped, 27-40 nm in diameter, has a genome containing single-stranded RNA, replicates in the cytoplasm of the host cell, and is not cultivable. Genetic and antigenic diversity is an important characteristic of noroviruses. Genetic variability is likely to be responsible for repeated infections during a lifetime and high attack rates in all age groups during outbreaks. The prototype strain Norwalk virus caused an outbreak of gastroenteritis in a school in Norwalk, Ohio in 1968. Currently at least 4 norovirus genogroups (GI, GII, GIII, and GIV) have been identified, and these have been divided into at least 20 genetic clusters.
Transmission is by feco-oral route, through consumption of fecally contaminated water or food, or by direct person-to-person spread. Shellfish harvested from fecally contaminated waters pose a special risk, as they possess the capacity to concentrate viruses through filtration. Contaminated fomites can be a source of infection. Vomitus also contains the virus, and droplets resulting from aerosolization of vomitus can be infective. Noroviruses are highly contagious and as few as 10 viral particles are sufficient to produce infection. The infection is often self-limited; rehydration by intravenous fluids is required in severe cases.
A reverse-transcriptase polymerase chain reaction (RT-PCR) has been developed and is used by many state public health laboratories in the U.S. for detection of norovirus in stool and vomitus samples. The test can be used to detect norovirus in shellfish and water samples as well. Other detection assays for noroviruses include enzyme immunoassay (EIA), electron microscopy, and immune electromicroscopy (IEM). Enzyme-linked immunosorbent (ELISA) assays developed for detection of IgM antibodies are not widely used due to limitations in detecting immune responses to a variety of antigenic types.

Question 6

A sexually active adolescent girl presented with fever, malaise, and painful vesiculo-ulcerative lesions of the genitalia of 3 days duration. Clinical diagnosis was suggestive of a viral infection. In the microbiology laboratory, material from the lesion was tested and found positive for a viral antigen by direct fluorescent antibody (DFA) test. This etiological viral agent is likely to possess what characteristic?

1 Grows only on human fibroblastic cells in vitro
2 Is an RNA virus with a long replication cycle of >48 hours
3 Remains latent in lymphoid tissues
4 Produces cytoplasmic inclusions in infected cells
5 Has glycoprotein G, an envelope protein that elicits type-specific antibodies

Answer 6

Has glycoprotein G, an envelope protein that elicits type-specific antibodies

The patient’s symptoms are suggestive of genital herpes, a widely prevalent sexually transmitted viral infection.
The major causative agent of genital herpes is Herpes simplex type 2 (HSV 2), accounting for 70-90% of primary genital herpes. Herpes simplex type 1 (HSV-1) also can cause genital herpes, though is mainly associated with oro-pharyngeal infections. Both types share a significant number of common antigens. An exception is Glycoprotein G, an envelope protein that elicits type-specific antibodies. Tests based on the recognition of antibodies to glycoprotein G antigens of HSV-1 (gG-1) and HSV-2 (gG-2) accurately distinguishes between HSV-1 and HSV-2 infections. Recurrence of genital herpes in HSV-2 infection is much more than in infection by HSV-1. High rates of HSV-2 infection are seen in HIV type-1 infected persons. Differentiation of the types and detection of HSV-2 infections is important in assessment of prognosis, management, and counseling of patients.
Other features listed are not characteristics of Herpes simplex virus.
Herpes simplex is a DNA virus, with the virus having a short replication cycle requiring only 8-16 hours for completion. Though human diploid fibroblasts are often preferred for growing the virus, it can grow in a variety of tissue culture cells and also on chorioallantoic membrane of chick embryo. The virus produces intranuclear eosinophilic inclusions in the infected cells, and the site of latency is a sensory ganglion.
In primary genital herpes, appearance of vesiculo-ulcerative lesions is often associated with systemic symptoms. Virus remains latent in sacral ganglia and leads to recurrent infections, mostly in HSV-2 infections. Asymptomatic infections are common. Both symptomatic and asymptomic infections serve as reservoirs of the virus.
Genital herpes during pregnancy presents great risk of transmitting infection to the newborn, resulting in neonatal herpes. HSV2 infection is known to enhance HIV susceptibility and subsequent sexual transmission because of the break in mucosal surface caused by the ulcerative lesions. Progressive disease and severe extensive lesions are seen in immunocompromised individuals.
Laboratory diagnosis of genital herpes is mainly based on virological tests and type-specific serological assays.
Virological tests include detection of viral antigen by direct fluorescent antibody test (DFA), viral culture, and Polymerase chain reaction (PCR) assay for detection and identification of the virus type. DFA does not identify HSV type and is less sensitive. PCR and culture yield positive results only during phases of active infection. Culture, though highly specific, is less sensitive. PCR is not widely available for use.
Type-specific serology using glycoprotein G antigens (gG-1 and gG-2) is recommended for confirming or establishing clinical diagnosis in symptomatic patients with negative culture and antigen testing and those with atypical presentations. The assays are used also for screening of high-risk populations. Enzyme Linked Immunosorbent Assay (ELISA), immunoblot tests, and a rapid membrane-based immunoassay for HSV-2 are available for detection of type-specific antibodies.
Acyclovir, famciclovir, and valacyclovir are drugs used for treatment of genital herpes. They reduce subclinical viral shedding and decrease frequency and severity of recurrent outbreaks.

Question 7

A 6-year-old girl presents with severe diarrhea and abdominal pain. A stool sample is analyzed by RT-PCR for RNA-dependent RNA polymerase and the result is negative. What is most likely responsible for this child’s symptoms?

1 Rotavirus
2 Influenza A virus
3 Poliovirus
4 B19V
5 Adenovirus

Answer 7

Adenovirus

The syndrome and PCR findings are most consistent with adenovirus infection. Adenovirus is a very common cause of diarrhea and vomiting in children. Since it is a DNA virus, it does not encode an RNA-dependent RNA polymerase.
Although rotavirus is the most common cause of diarrhea and vomiting in children, it is a dsRNA virus and it does encode RNA-dependent RNA polymerase.
Influenza A is mainly a respiratory disease. Although it can be associated with abdominal discomfort in children, it not typically associated with predominantly gastrointestinal symptoms.
Poliovirus, the etiological agent of polio, causes flu-like symptoms that can progress to paralysis; its main manifestations are not diarrhea and vomiting.
Parvovirus B19 is a DNA virus; it does not encode RNA-dependent RNA polymerase. Additionally, it causes erythema infectiosum (“slapped cheek” syndrome) and sometimes aplastic anemia rather than diarrhea and vomiting.

Question 8

You are studying a virus isolated in the laboratory from mouse epithelial cells. The genetic material from this virus is examined and found to contain adenine, guanine, cytosine, and uracil, but no thymine. You begin to study the mechanism of replication of this virus. Based on the fact that the genetic material of this virus contains uracil, what is the enzyme unique to these types of viruses that helps form double-stranded DNA?

1 Guanylate cyclase
2 Integrase
3 Reverse transcriptase
4 Topoisomerase
5 DNA ligase

Answer 8

Reverse transcriptase

The correct answer is reverse transcriptase because of the fact that it contains uracil, which indicates that it is an RNA virus. A double-stranded DNA virus is formed from an RNA virus by reverse transcriptase. A retrovirus is an infectious particle consisting of an RNA genome packaged in a protein capsid surrounded by a lipid envelope. This lipid envelope contains polypeptide chains, including receptor-binding proteins that link to the membrane receptors of the host cell, initiating the process of infection. In order to replicate, its genetic material (RNA) must first be converted to a DNA molecule by the enzyme reverse transcriptase. This enzyme, which is found in the virus particle, is a DNA polymerase that uses an RNA molecule as a template to synthesize DNA, resulting in an RNA/DNA double helix.
Further enzyme action leads to the synthesis of a DNA double helix using the RNA/DNA template. This DNA helix can then integrate into the host chromosome and be transcribed into RNA molecules coding for capsid proteins, envelope proteins, and the reverse transcriptase. This integration into the host DNA is carried out by the viral integrase. Integration into the host chromosome is required for the synthesis of new viral RNA molecules. A host cell RNA polymerase is responsible for this transcription. Many new virus particles are then assembled containing the RNA molecule and the enzyme reverse transcriptase.
Guanylate cyclase is an enzyme unrelated to transcription and translation. It is involved in the conversion of guanosine triphosphate (GTP) to cyclic guanosine monophosphate.
Topoisomerases are involved in unwinding the DNA to allow transcription and replication to occur. The DNA topology is adjusted by making temporary cuts in the DNA to allow unwinding.
DNA ligase helps bond DNA-strands, which have a double-strand break. It plays a significant role in DNA replication and repair.

Question 9

Ribosomes are usually absent in viruses, with the exception of

1 Arenavirus
2 Retrovirus
3 Herpesvirus
4 Togavirus
5 Adenovirus

Answer 9

Arenavirus

Arenavirus posses a few nonfunctional ribosomes. Ribosomes are absent in retrovirus, herpesvirus, togavirus and adenovirus.

Question 10

Viruses that are made up of lipoprotein envelope are generally

1 Less stable
2 More stable
3 Pathogenic
4 Viroids
5 Pseudoviruses

Answer 10

Less stable

Viruses that are made of lipoprotein envelope are generally less stable being more sensitive to heat, detergents, and lipid solvents such as alcohol and ether. They are not more stable or pathogenic. Viroids are atypical virus-like particles that are made up solely of single molecules of circular RNA without a protein coat. Pseudoviruses contain host cell DNA instead of viral DNA in the capsid.

Question 11

The viral envelope is composed of

1 Lipoprotein
2 Peptidoglycan
3 Lipopolysaccharide
4 Teichoic acid
5 Nucleoid

Answer 11

Lipoprotein

The viral envelope is composed of lipoprotein which is composed of lipid derived from the host cell membrane and protein that is virus-specific. Peptidoglycan is found in bacterial cell wall and is composed of peptides and sugars. Lipopolysaccharides are found in the outer cell wall of gram negative bacteria. Teichoic acids are polymers of glycerol phosphate or ribitol phosphate located in the outer layer of gram positive cell wall. Nucleoid is an area of cytoplasm where DNA is located.

Question 12

Which one of the following statements best describes prions?

1 They are infectious particles composed solely of proteins
2 They are composed of viral nucleic acids but cannot replicate without a helper virus
3 They contain host cell DNA instead of viral DNA within the capsid
4 They consist solely of a single molecule of circular RNA without a protein coat or envelope
5 They are protein particles that generate a strong immune response

Answer 12

They are infectious particles composed solely of proteins

Prions are infectious particles composed solely of proteins. They are not composed of viral nucleic acids and do not need a helper virus to replicate. They do not contain host cell DNA instead of viral DNA within the capsid; they do not consist solely of a single molecule of circular RNA without a protein coat or envelope; and they are not protein particles that generate a strong immune response.

Question 13

During the lysogenic cycle, the viral DNA is located in the

1 Host cell chromosome
2 Extrachromosomal element
3 Plasmid
4 Host cell wall
5 Host cell endoplasmic reticulum

Answer 13

Host cell chromosome

During the lysogenic cycle, the viral DNA is located in the host cell chromosome and not in extrachromosomal element, plasmid, host cell wall, or host cell endoplasmic reticulum.

Question 14

Lysogenic phase of viral growth cycle occurs if the gene product that is encoded by the cI gene predominates. This gene encodes for a

1 Repressor
2 Antagonizer of repressor
3 Reverse transcriptase
4 RNA polymerase
5 DNA polymerase

Answer 14

Repressor

The cI gene product encodes for a repressor, which turns off transcription of early genes so that lysogenic phase can ensue. Transcription is inhibited by binding of the repressor to two operator sites that control early protein synthesis. If the product of the cro gene that encodes for the antagonizer of the repressor predominates, it prevents synthesis of sufficient repressor and replication and lysis of the cell results.
Repressor can also prevent replication of additional lambda phages that infect subsequently. This is called immunity and is specifically directed against lambda phage, because the repressor binds only to the operator sites in lambda DNA and other phages are not affected.

Question 15

Which of the following accurately describes the correct sequence of steps in viral infection and replication?

1 Uncoating, attachment, biosynthesis, penetration
2 Attachment, uncoating, penetration, biosynthesis
3 Attachment, penetration, uncoating, biosynthesis
4 Uncoating, attachment, penetration, biosynthesis
5 Uncoating, penetration, attachment, biosynthesis

Answer 15

Attachment, penetration, uncoating, biosynthesis

The first step requires a compatible union between sites on the virus and target cell, and likely involves electrostatic interactions. The surface site on the virus may be a spike or fiber of a specific protein. The receptor site on the target cell most typically is a glycoprotein, and may be shared by related members of the same virus group.
Penetration of the cell can occur via four mechanisms. Some viruses may be phagocytized. Alternatively, the viral lipoprotein of the envelope may fuse with the cell membrane. Thirdly, the virus may interact with cell membrane receptor sites, a process in which host cell enzymes start uncoating at the cell membrane, resulting in the nucleic acid (and occasionally its associated polymerase) escaping into the cell. Finally, direct penetration of the intact virus through the cell membrane into the cytoplasm occurs in some viruses.
Prior to replication, the viral genome must be extricated from all of the surrounding material. The destruction or disassembly of the capsid may commence while the virion is adsorbing to and penetrating through the cell. For some enveloped viruses, elimination of this coating occurs at the surface of the cells.
The location of viral synthesis is variable with the nature of the genome (DNA or RNA) and the family or group to which the virus belongs. The DNA of deoxyriboviruses is synthesized in the nucleus of the infected cell, while the protein components are translated in the cytoplasm. The poxviruses represent the exception, as all macromolecular synthesis occurs cytoplasmically. Similar to the poxviruses, the viral components of most of the riboviruses are synthesized in the cytoplasm. But here, too, there are exceptions: nuclear synthesis of some viral macromolecules occurs in the orthomyxoviridae (the group including influenza) and some of the paramyxoviridae and retroviridae.

Question 16

Varicella is transmitted primarily by

1 Respiratory droplets
2 Sexual contact
3 Body fluids
4 Arthropods
5 Direct skin contact

Answer 16

Respiratory droplets

Varicella is caused by varicella-zoster virus and is transmitted primarily by respiratory droplets. The initial infection is in the respiratory tract. It spreads via the blood to the internal organs, such as liver, and then to the skin.

Question 17

Infectious mononucleosis can be caused by what?

1 Herpes virus
2 Epstein Barr virus
3 Cytomegalo virus
4 Rickettsiae
5 Adeno virus

Answer 17

Epstein Barr virus

The Epstein Barr virus causes infectious mononucleosis associated with the Burkitts lymphoma in East African children. The virus is found in human oropharynx and B lymphocytes. It is transmitted primarily by saliva. The infection begins in the pharyngeal epithelium, spreads to the cervical lymph nodes, then travels through the blood to the liver and spleen.

Question 18

For which of the following viruses is assay by viral enzymes particularly useful?

1 Influenza
2 Parainfluenza
3 Mumps virus
4 Hepatitis B virus
5 Retroviridae

Answer 18

Hepatitis B virus

No suitable cell culture system is currently available for the hepatitis B virus. Fortunately, the hepatitis B virus produces a DNA-dependent polymerase that is virus specific. Influenza A, influenza B, mumps virus, and parainfluenza virus may be cultured in primary monkey kidney cells. Influenza A, B, and C all may be cultured in eggs. Influenza A and B may be detected by hemadsorption, cytopathic effect, and hemagglutination; Influenza C may be detected by hemagglutination. Retroviridae may be cultured in T lymphocytes with methods of detection of transformation, reverse transcriptase, cytopathic effect, or immunofluorescence.

Question 19

Which of the following methods is the most precise, universally useful technique for enumerating infective virus particles?

1 Pock assay
2 Plaque or Focal Assay
3 Electron microscopy Hemagglutination
4 Quantal Assay

Answer 19

Plaque or Focal Assay

The keys to this question are the terms “universally useful” and “infective.” Some of the described methods lead to the counting of both viable and nonviable particles, as described below.
Electron microscopy is useful for enumerating purified virus particles present at high density. The addition of a known number of latex particles to the suspension, followed by the calculation of the ratio of those particles to viral particles, provides an accurate count. Of course, this technique has the disadvantage that viable and nonviable particles cannot be differentiated. Equally important, very few diagnostic laboratories, and indeed not all research laboratories, have ready access to an electron microscope.
The plaque assay is the most precise measure of infectivity. The basis of this technique is the formation of clear zones, plaques or foci, in a monolayer of host cells. Serial dilutions of the virus are added to a monolayer of cells known to be infected by the cells (for example, MDCK cells are used for influenza). Most commonly after the virus has been allowed to adsorb onto the cells, an agar overlay is added to prevent dispersion of the virus. This ensures that each plaque represents only a single initial virus particle. For viruses which only infect contiguous cells without releasing virions into the surrounding medium, the agar may be replaced by a liquid.
Certainly not applicable for all viruses, the pock assay involves the counting of localized lesions (pocks) that form on the chorioallantoic membrane (CAM) of the embryonated egg upon addition of known dilutions of the virus. As in the plaque assay, each lesion represents a single original virus particle.
Instead of providing a quantitative measure of viral infectivity, quantal assays provide only a “yes or no” result. In quantal assays, each viral replication cycle results in an amplification of the effects of each individual virus particle. The virus is serially diluted, and appropriate cells are incubated with a known volume of each dilution. The endpoint for these assays may be negative effects, including morbidity in animals and development of lesions on either the chorioallantoic membrane or on the embryo of eggs. Following the incubation period, each target animal, or sample, is examined for a +/- response.

Question 20

Which one of the following is the largest virus?

1 Poxvirus
2 Parvovirus
3 Hepadnavirus
4 Papovavirus
5 Adenovirus

Answer 20

Poxvirus

The largest known virus is the poxvirus that has a particle size of 250x400nm. The parvovirus particle size is 22nm, hepadnavirus is 42nm, papovavirus is 55nm, and adenovirus is 75nm.

Question 21

Inoculation of lymphocytic choriomeningitis virus into the brain of an immunosuppressed adult mouse results in

1 Disease followed by shorter life span
2 Disease followed by complete recovery
3 Disease followed by carrier status
4 Death
5 No effect

Answer 21

No effect

Inoculation of lymphocytic choriomeningitis virus into the brain of immunosuppressed adult mice has no effect. However, inoculation into the brain of a normal mouse results in death due to immune attack by cytotoxic T cells on the viral antigens in the cell membranes, rather than by virus-induced inhibition of cell functions. It does not cause disease followed by either a shorter life span, complete recovery, carrier status, or death.

Question 22

Which one of the following is an example of a chronic carrier infection?

1 Hepatitis B
2 Neonatal rubella virus
3 Cytomegalovirus
4 Retrovirus
5 Togavirus

Answer 22

Hepatitis B

Hepatitis B is an example of a chronic carrier infection where a carrier state can follow an asymptomatic infection, as well as actual disease. Neonatal rubella virus, cytomegalovirus, retrovirus, and togavirus do not cause chronic carrier infection.

Question 23

Which one of the following drugs inhibits viral protein synthesis?

1 Methisazone
2 Azidothymidine
3 Dideoxyadenosine
4 Foscarnet
5 Acyclovir

Answer 23

Methisazone

Methisazone inhibits viral protein synthesis of poxviruses such as small pox and vaccinia virus. Azidothymidine is an inhibitor of retrovirus growth and inhibits chain termination during DNA synthesis. Dideoxyadenosine is a nucleoside analogue that causes chain termination during DNA synthesis. Foscarnet is a pyrophosphate analogue that inhibits the DNA polymerase of all herpes viruses and reverse transcriptase of HIV. Acyclovir (Zovirax) is a nucleoside analogue with a 3-carbon analogue in place of the normal sugar ribose.

Question 24

Herpes virus can be detected by the Tzanck smear of the skin lesion. This test stains for the presence of which one of the following?

1 Multinucleated giant cells
2 Inclusion bodies
3 Dead cells
4 Herpes DNA
5 Herpes cell envelope

Answer 24

Multinucleated giant cells

The Tzanck smear stains for the presence of multinucleated giant cells that are formed as a result of fusion of cell membranes due to insertion of viral proteins into the membrane. Tzanck smear does not detect the presence of inclusion bodies, dead cells, herpes DNA, or cell envelope.

Question 25

Which one of the following viruses causes gingivostomatitis? ## Footnote 1 Herpes simplex virus-1 2 Herpes simplex virus-2 3 Varicella zoster virus 4 Epstein Barr virus 5 Cytomegalovirus

Answer 25

Herpes simplex virus-1 ## Footnote Herpes simplex virus-1 causes gingivostomatitis. Herpes simplex virus-2 causes herpes of the genitals, varicella zoster causes varicella, Epstein-Barr virus causes infectious mononucleosis, and cytomegalovirus causes congenital infections.

Question 26

Which of the following statements best describes the relationship between varicella and zoster? ## Footnote 1 Varicella is the primary disease, and zoster is the recurrent form 2 Zoster is the primary disease, and varicella is the secondary disease 3 Varicella and zoster are the same disease 4 Varicella and zoster occur at the same time in an individual 5 Varicella and zoster are unrelated

Answer 26

Varicella is the primary disease, and zoster is the recurrent form ## Footnote Varicella and zoster are caused by the varicella zoster virus. Varicella is the primary disease, and zoster is the recurrent form of the disease that occurs in immunocompromised adults. Zoster is not the primary disease and varicella the secondary disease; they are not the same disease, and they are related because they are caused by the same virus.

Question 27

How is the recombination of RNA segments from 2 different influenza virus strains described? ## Footnote 1 Antigenic shift 2 Antigenic drift 3 Peptidoglycan 4 Teichoic acids 5 Prions

Answer 27

Antigenic shift ## Footnote Antigenic shift and antigenic drift can be found in the influenza virus. Antigenic shift is a process by which 2 or more different types of influenza A combine to form a virus radically different from the ancestor strains. Antigenic shift occurs in 2 ways. 1. Antigenic shift can occur through genetic recombination, or reassortment, when 2 or more different influenza A viruses infect the same host cell and combine their genetic material. 2. Qn influenza A virus can jump from 1 type of organism, usually a bird, to another type of organism, such as a human, without undergoing major genetic change. A point mutation that leads to an amino acid change and altered antigenic sites so that the virus is no longer recognized by the host immune system is called antigenic drift. Peptidoglycan and teichoic acids are components of the bacterial cell wall and prions are infectious protein particles.

Question 28

Paramyxoviruses possess hemagglutinin and neuraminidase that are present on the ## Footnote 1 Same spike 2 Different spikes 3 Nucleus 4 Golgi bodies 5 Endoplasmic reticulum

Answer 28

Same spike ## Footnote Paramyxoviruses possess hemagglutinin and neuraminidase that are present on the same spike. This is in contrast to the orthomyxoviruses that possess hemagglutinin and neuraminidase on different spikes.

Question 29

Rubella virus is a member of the family of: ## Footnote 1 Togavirus 2 Herpes virus 3 Neisseriae 4 Adenovirus 5 Picornavirus

Answer 29

Togavirus ## Footnote Rubella virus is a member of the togavirus family and not the herpes virus, neisseriae, adenovirus, and picornavirus.

Question 30

Which one of the following is a test for detection of cell-bound or incomplete antibodies? ## Footnote 1 Antiglobulin test 2 Gram stain 3 Enzyme linked immunoassay 4 Radioimmunoassay 5 Gel diffusion test

Answer 30

Antiglobulin test ## Footnote Antiglobulin or Coombs test is used for the detection of cell-bound or incomplete antibodies that by themselves are incapable of agglutinating particles, but can bind to them firmly. By adding antibodies against globulin species, agglutination of the coated particles results. This test has the greatest application in the detection of various red blood cell antibodies in hemolytic anemias. Gram stain is used for the detection of bacteria. Enzyme linked immunoassay, radioimmunoassay, and gel diffusion tests are not used for the detection of cell-bound or incomplete antibodies.

Question 31

Which of the following pairs of viruses are most closely related? ## Footnote 1 Poliovirus and Orbivirus 2 Enteroviruses and Rotavirus 3 Rotavirus and Echoviruses 4 Enteroviruses and Rhinoviruses 5 Rhinoviruses and Orbivirus

Answer 31

Enteroviruses and Rhinoviruses ## Footnote Both the Enterovirus group, which includes the Poliovirus, Coxsackieviruses, and Echoviruses, and the Reoviridae, which includes the Reovirus, Orbivirus, and Rotavirus, have an RNA genome. The genomes of the former group are linear and single-stranded, whereas those of the later are double stranded and may be either linear or segmented. The Picornaviridae family of viruses contains the Enterovirus and the Rhinoviruses, which have numerous properties in common. Viruses of this family lack an envelope and are icosahedral with a diameter of 20nm. The genome is a single-strand RNA. The Enteroviruses are stable to acid, while the Rhinoviruses are sensitive.

Question 32

Which of the following are structurally most closely related to the influenza virus? ## Footnote 1 Retroviridae 2 Togaviridae 3 Paramyxoviruses 4 Coronaviridae 5 Rhabdoviridae

Answer 32

Paramyxoviruses ## Footnote Each of these viral families or groups has an RNA genome and envelope. The Paramyxoviruses are structurally the most closely related to influenza, since both are negative sense RNA viruses and many of the paramyxoviruses contain a neuraminidase and hemagglutinin. There are some notable differences, however. In the paramyxoviruses, both neuraminidase and hemagglutinin functions contained in a single glycoprotein on one type of spike, whereas in influenza, these functions are accomplished by two separate glycoproteins which on two types of spikes (except for Influenza C, which has both functions on a single glycoprotein). In addition, the genome is segmented in influenza, but not in the paramyxoviruses. The viruses in the Togaviridae and Coronaviridae families differ from the Influenza viruses in that they have a positive sense RNA genome. Viruses in the Rhabdoviridae family, which includes the vesicular stomatitis virus and the rabies virus, are bacilliform negative-stranded RNA viruses.

Question 33

These enveloped, pleomorphic, and ss-RNA viruses cause respiratory infections by droplet nuclei or contact transmission. These belong to the orthomyxovirus group and are called what? ## Footnote 1 Lentiviruses 2 Influenza virus 3 Parainfluenza virus 4 Respiratory syncytial virus

Answer 33

Influenza virus ## Footnote The influenza virus is a member of the orthomyxovirus group and is an enveloped ss-RNA virus. Lentiviruses are a group of retroviruses which include HIV-1. Parainfluenza virus and respiratory syncytial virus (RSV) belong to the paramyxovirus group.

Question 34

This large-enveloped ds-DNA virus is associated with 70% of the initial genital infections by this virus group. Clinically, these infections present with small erythematous papules which progress to open ulcerations. Infections can become latent and recurrent. Which virus is this? ## Footnote 1 HSV-1 2 HSV-2 3 HIV-1 4 HIV-2

Answer 34

HSV-2 ## Footnote Herpes simplex type 1 and 2 (HSV-1, HSV-2) are both large-enveloped DNA viruses which cause latent and recurrent infections. However, HSV-1 is primarily associated with infections of the pharynx, skin, and central nervous system. On the other hand, HSV-2 is primarily associated with genital infections, representing approximately 70% of all such initial infections. HSV-2 infections recur more often as well. Human immunodeficiency virus type 1 and 2 (HIV-1 and HIV-2) are retroviruses with plus-strand RNA genomes. Both of these can be passed by sexual contact and result in long-term infection of multiple cells and tissues. Both can also give rise to acquired immune deficiency syndrome or AIDS, however HIV-1 is associated with a long-term infection which has been virtually 99% fatal after 10-15 years. Recent research has illustrated that a small number of individuals may be infected with somewhat less virulent strains and these individuals do not follow the normal time-course to AIDS. HIV-2 is associated with a far less virulent infection and may include a much larger percentage of "none-progressing" individuals as well.

Question 35

Viruses are ## Footnote 1 Free living saprophytes 2 Obligate intracellular parasites 3 Composed of DNA, as well as RN 4 Smallest free living cells 5 Capable of making their own proteins

Answer 35

Obligate intracellular parasites ## Footnote Viruses are the smallest organism known and are not free living cells, but are obligate intracellular parasites. They were called filterable agents as they can pass through the filters designed to retain bacteria. Viral genome is made up of either DNA or RNA, but not both. The viral genome is packaged into a protein coat called capsid. Capsid together with nucleic acid is called nucleocapsid. Nucleocapsid can be surrounded by a lipid called envelope. Viruses can not make their own protein or energy. Viruses require host cell biochemical machinery for energy and to make proteins. Viruses do not reproduce by binary fission or division. Viral reproduction occurs by self-assembly of individual components.

Question 36

Which of the following is the correct sequence of viral replication? ## Footnote 1 Attachment, uncoating, penetration, protein synthesis, assembly, and release 2 Attachment, penetration, uncoating, protein synthesis, assembly, and release 3 Uncoating, attachment, penetration, protein synthesis, assembly, and release 4 Penetration, attachment, protein synthesis, uncoating, assembly, and release 5 Penetration, uncoating, attachment, protein synthesis, assembly, and release

Answer 36

Attachment, penetration, uncoating, protein synthesis, assembly, and release ## Footnote Viral replication takes place in several stages. Once the virus recognizes the target cell, it binds to the cell. The viral attachment protein present on the surface of virion interacts with the cell receptor. Following attachment the virus can penetrate the cell by process of endocytosis or fusion. In the step of uncoating the capsid the envelope is removed and viral nucleic acid is released inside the host cell, so the viral genes become available for transcription. In the protein synthesis step the process differs according to type of virus and the structure of genome. RNA virus mostly replicates in the cytoplasm. Plus-strand RNA viruses initiate protein synthesis. Minus-strand RNA virus, double-stranded RNA viruses, and DNA viruses initiate nucleic acid synthesis. Protein synthesis in DNA virus replication is divided into early phase and late phase. Once the replication is over the newly synthesized viral protein and nucleic acid is assembled inside the cells. The capsomers are self assembled into capsid. In enveloped virus the viral envelope is added from the cell membrane and becomes associated with nucleocapsid. The newly assembled virus is released from the cell by budding or cell lysis.

Question 37

Which of the following RNA viruses replicate in the nucleus rather than in the cytoplasm? ## Footnote 1 Retroviruses 2 Picornaviruses 3 Togaviruses 4 Reoviruses 5 Arenaviruses

Answer 37

Retroviruses ## Footnote Viral replication of majority of RNA viruses takes place in the cytoplasm. Retroviruses have a nuclear phase for their replication via a DNA intermediate. These viruses carry 2 copies of genome, 2 tRNA molecule, and an enzyme reverse transcriptase. Diploid genome has an inverted dimer of plus sense ssRNA. Reverse transcriptase uses tRNA molecule to make DNA copy. The viral DNA circularizes and integrates into the host genome. This integrated DNA is used as template for transcription of viral RNA.

Question 38

Which of the following viruses is the smallest virus? ## Footnote 1 Poxviruses 2 Reoviruses 3 Parvoviruses 4 Picornaviruses 5 Papovaviruses

Answer 38

Parvoviruses ## Footnote Poxviruses are the largest viruses in the category and parvoviruses are the smallest. Parvoviruses measure about 18 to 26 nm in diameter and contains single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. Parvoviruses do not contain envelope and have icosahedral symmetry. B19 is a parvovirus which is member of genus Erythrovirus and is associated with erythema infectiosum, a human disease. This virus requires mitotically active cells for growth, such as fresh human bone marrow cells, embryonic cells, and erythroid leukemia cells.

Question 39

The only double-stranded RNA viruses belongs to the family ## Footnote 1 Picornaviridae 2 Retroviridae 3 Arenaviridae 4 Togaviridae 5 Reoviridae

Answer 39

Reoviridae ## Footnote Most of the families of RNA viruses infecting human consists of single strand of RNA, except the family Reoviridae. The virions in Reoviridae family consists of double stranded RNA, made up of 10-12 segments that separates them from other RNA viruses. Reoviruses are naked with icosahedral symmetry. Reoviruses replicate in the cytoplasm and are released by cell lysis. Reoviridae family comprises of genus: Orthoreovirus. Orbivirus. Rotavirus. Orthoreovirus is associated with mild upper respiratory disease, gastrointestinal infection, and biliary atresia. Orbivirus causes febrile illness accompanied by headache and myalgia. Orbivirus is the etiological agent of Colorado tick fever that is transmitted by the wood tick. Rotaviruses are implicated in epidemic diarrhea in young children.

Question 40

Human T-cell lymphotropic viruses are ## Footnote 1 Single stranded DNA with naked icosahedral nucleocapsid 2 Linear double stranded DNA with naked icosahedral nucleocapsid 3 Double stranded circular DNA with naked icosahedral nucleocapsid 4 Double stranded linear DNA with enveloped complex nucleocapsid 5 Double stranded linear DNA with enveloped icosahedral nucleocapsid 6 Double stranded RNA with naked icosahedral nucleocapsid 7 Single stranded linear RNA with naked icosahedral nucleocapsid 8 Single stranded linear RNA with enveloped icosahedral nucleocapsid 9 Single stranded RNA with reverse transcriptase and diploid genome 10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid

Answer 40

Single stranded RNA with reverse transcriptase and diploid genome ## Footnote Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA. Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer. Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host. Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease. Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans. Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane. Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA. Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule. Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm. Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.

Question 41

Papillomavirus are: ## Footnote 1 Single stranded DNA with naked icosahedral nucleocapsid. 2 Linear double stranded DNA with naked icosahedral nucleocapsid. 3 Double stranded circular DNA with naked icosahedral nucleocapsid. 4 Double stranded linear DNA with enveloped complex nucleocapsid. 5 Double stranded linear DNA with enveloped icosahedral nucleocapsid. 6 Double stranded RNA with naked icosahedral nucleocapsid. 7 Single stranded linear RNA with naked icosahedral nucleocapsid. 8 Single stranded linear RNA with enveloped icosahedral nucleocapsid. 9 Single stranded RNA with reverse transcriptase and diploid genome. 10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid.

Answer 41

Double stranded circular DNA with naked icosahedral nucleocapsid. ## Footnote Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA. Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer. Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host. Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease. Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans. Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane. Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA. Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule. Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm. Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.

Question 42

Sandfly fever virus is a ## Footnote 1 Single stranded DNA with naked icosahedral nucleocapsid 2 Linear double stranded DNA with naked icosahedral nucleocapsid 3 Double stranded circular DNA with naked icosahedral nucleocapsid 4 Double stranded linear DNA with enveloped complex nucleocapsid 5 Double stranded linear DNA with enveloped icosahedral nucleocapsid 6 Double stranded RNA with naked icosahedral nucleocapsid 7 Single stranded linear RNA with naked icosahedral nucleocapsid 8 Single stranded linear RNA with enveloped icosahedral nucleocapsid 9 Single stranded RNA with reverse transcriptase and diploid genome 10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid

Answer 42

Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid ## Footnote Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA. Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer. Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host. Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease. Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans. Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane. Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA. Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule. Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm. Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.

Question 43

Parvovirus is a ## Footnote 1 Single stranded DNA with naked icosahedral nucleocapsid 2 Linear double stranded DNA with naked icosahedral nucleocapsid 3 Double stranded circular DNA with naked icosahedral nucleocapsid 4 Double stranded linear DNA with enveloped complex nucleocapsid 5 Double stranded linear DNA with enveloped icosahedral nucleocapsid 6 Double stranded RNA with naked icosahedral nucleocapsid 7 Single stranded linear RNA with naked icosahedral nucleocapsid 8 Single stranded linear RNA with enveloped icosahedral nucleocapsid 9 Single stranded RNA with reverse transcriptase and diploid genome 10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid

Answer 43

Single stranded DNA with naked icosahedral nucleocapsid ## Footnote Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA. Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer. Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host. Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease. Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans. Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane. Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA. Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule. Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm. Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.

Question 44

Rotaviruses are ## Footnote 1 Single stranded DNA with naked icosahedral nucleocapsid 2 Linear double stranded DNA with naked icosahedral nucleocapsid 3 Double stranded circular DNA with naked icosahedral nucleocapsid 4 Double stranded linear DNA with enveloped complex nucleocapsid 5 Double stranded linear DNA with enveloped icosahedral nucleocapsid 6 Double stranded RNA with naked icosahedral nucleocapsid 7 Single stranded linear RNA with naked icosahedral nucleocapsid 8 Single stranded linear RNA with enveloped icosahedral nucleocapsid 9 Single stranded RNA with reverse transcriptase and diploid genome 10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid

Answer 44

Double stranded RNA with naked icosahedral nucleocapsid ## Footnote Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA. Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer. Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host. Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease. Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans. Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane. Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA. Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule. Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm. Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.

Question 45

Rubella virus is ## Footnote 1 Single stranded DNA with naked icosahedral nucleocapsid 2 Linear double stranded DNA with naked icosahedral nucleocapsid 3 Double stranded circular DNA with naked icosahedral nucleocapsid 4 Double stranded linear DNA with enveloped complex nucleocapsid 5 Double stranded linear DNA with enveloped icosahedral nucleocapsid 6 Double stranded RNA with naked icosahedral nucleocapsid 7 Single stranded linear RNA with naked icosahedral nucleocapsid 8 Single stranded linear RNA with enveloped icosahedral nucleocapsid 9 Single stranded RNA with reverse transcriptase and diploid genome 10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid

Answer 45

Single stranded linear RNA with enveloped icosahedral nucleocapsid ## Footnote Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA. Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer. Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host. Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease. Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans. Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane. Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA. Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule. Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm. Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.

Question 46

Adenoviruses consist of ## Footnote 1 Single stranded DNA with naked icosahedral nucleocapsid 2 Linear double stranded DNA with naked icosahedral nucleocapsid 3 Double stranded circular DNA with naked icosahedral nucleocapsid 4 Double stranded linear DNA with enveloped complex nucleocapsid 5 Double stranded linear DNA with enveloped icosahedral nucleocapsid 6 Double stranded RNA with naked icosahedral nucleocapsid 7 Single stranded linear RNA with naked icosahedral nucleocapsid 8 Single stranded linear RNA with enveloped icosahedral nucleocapsid 9 Single stranded RNA with reverse transcriptase and diploid genome 10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid

Answer 46

Linear double stranded DNA with naked icosahedral nucleocapsid ## Footnote Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA. Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer. Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host. Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease. Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans. Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane. Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA. Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule. Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm. Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.

Question 47

Smallpox virus is ## Footnote 1 Single stranded DNA with naked icosahedral nucleocapsid 2 Linear double stranded DNA with naked icosahedral nucleocapsid 3 Double stranded circular DNA with naked icosahedral nucleocapsid 4 Double stranded linear DNA with enveloped complex nucleocapsid 5 Double stranded linear DNA with enveloped icosahedral nucleocapsid 6 Double stranded RNA with naked icosahedral nucleocapsid 7 Single stranded linear RNA with naked icosahedral nucleocapsid 8 Single stranded linear RNA with enveloped icosahedral nucleocapsid 9 Single stranded RNA with reverse transcriptase and diploid genome 10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid

Answer 47

Double stranded linear DNA with enveloped complex nucleocapsid ## Footnote Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA. Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer. Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host. Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease. Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans. Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane. Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA. Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule. Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm. Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.

Question 48

Enteroviruses contain ## Footnote 1 Single stranded DNA with naked icosahedral nucleocapsid 2 Linear double stranded DNA with naked icosahedral nucleocapsid 3 Double stranded circular DNA with naked icosahedral nucleocapsid 4 Double stranded linear DNA with enveloped complex nucleocapsid 5 Double stranded linear DNA with enveloped icosahedral nucleocapsid 6 Double stranded RNA with naked icosahedral nucleocapsid 7 Single stranded linear RNA with naked icosahedral nucleocapsid 8 Single stranded linear RNA with enveloped icosahedral nucleocapsid 9 Single stranded RNA with reverse transcriptase and diploid genome 10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid

Answer 48

Single stranded linear RNA with naked icosahedral nucleocapsid ## Footnote Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA. Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer. Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host. Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease. Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans. Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane. Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA. Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule. Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm. Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.

Question 49

Herpes simplex virus contains ## Footnote 1 Single stranded DNA with naked icosahedral nucleocapsid 2 Linear double stranded DNA with naked icosahedral nucleocapsid 3 Double stranded circular DNA with naked icosahedral nucleocapsid 4 Double stranded linear DNA with enveloped complex nucleocapsid 5 Double stranded linear DNA with enveloped icosahedral nucleocapsid 6 Double stranded RNA with naked icosahedral nucleocapsid 7 Single stranded linear RNA with naked icosahedral nucleocapsid 8 Single stranded linear RNA with enveloped icosahedral nucleocapsid 9 Single stranded RNA with reverse transcriptase and diploid genome 10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid

Answer 49

Double stranded linear DNA with enveloped icosahedral nucleocapsid ## Footnote Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA. Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer. Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host. Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease. Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans. Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane. Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA. Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule. Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm. Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.

Question 50

Which of the following viruses consists of circular DNA that is partially double stranded and partially single stranded? ## Footnote 1 Hepatitis B virus 2 Varicella-zoster virus 3 Lassa fever virus 4 Epstein-Barr virus 5 Respiratory syncytial virus

Answer 50

Hepatitis B virus ## Footnote Hepatitis B virus is the DNA virus that is part of the Hepadnaviridae family. The characteristic feature of the virus from this family is that the genome consists of a circular DNA that is part double stranded and part single stranded. The virions are spherical particles with an envelope. Hepatitis B virus consists of icosahedral core within a closely adherent capsid that contains cellular lipid, glycoproteins, and a virus-specific surface antigen called Hepatitis B surface antigen (HBsAg). Respiratory syncytial virus is RNA virus that has linear single stranded nonsegmented RNA. Lassa fever virus has a circular single stranded RNA in 2 segments. Varicella-zoster virus and Epstein-Barr virus consist of a linear double stranded DNA.

Question 51

The incubation period for hepatitis B is approximately ## Footnote 1 1-3 days 2 5-10 days 3 10-20 days 4 15-40 days 5 50-160 days

Answer 51

50-160 days ## Footnote Hepatitis B is also called serum hepatitis and is caused by a DNA virus known as hepatitis B virus. It is transmitted primarily by parentral route with infected blood or blood products. The hepatitis B virus can also be transmitted by sexual contact or with contaminated body fluids. Hepatitis B has a longer incubation period which is approximately 50-160 days. The onset of disease is gradual and the infection can be acute or self-limiting or can lead to persistent viremia and chronic liver disease with immunologic complications. Hepatitis A is transmitted by feco-oral route and has an incubation period of 15-40 days.

Question 52

Which of the following serological markers is first to appear during the incubation period of hepatitis B? ## Footnote 1 HBcAg 2 HBsAg 3 Anti HBcAg-IgM 4 Anti HBsAg 5 Anti HBeAg

Answer 52

HBsAg ## Footnote The course of hepatitis B viral infection and nature of the disease can by described by detection of serological markers in the laboratory using ELISA or EIA. HBsAg is the first to appear and can be detected during the incubation period of hepatitis B. The test for detection of HBcAg is not yet available. Anti-HBsAg and anti-HBeAg appear after disappearance of HBsAg. Anti-HBcAg-IgM along with HBsAg can be used as an indicator of acute infection.

Question 53

Which of the following is an enveloped RNA virus from the family Flaviviridae and is the major cause of post-transfusion hepatitis? ## Footnote 1 Hepatitis A virus 2 Hepatitis B virus 3 Hepatitis C virus 4 Hepatitis D virus 5 Hepatitis E virus

Answer 53

Hepatitis C virus ## Footnote Hepatitis C is an enveloped icosahedral RNA virus with gene order characteristic of the family Flaviviridae. The genome of Hepatitis C is infectious and consists of a linear single stranded 9.5 kb molecule of RNA. The virus replicates in the cytoplasm. Hepatitis C is transmitted by paranteral and sexual routes. It is the most common cause of post-transfusion hepatitis. Hepatitis C is associated with acute infection, chronic liver disease, and cirrhosis. Hepatitis C viral infection may serve as a predisposing factor in primary hepatocellular carcinoma. Hepatitis B virus is an enveloped DNA virus that is part of the Hepadnaviridae family. The genome of Hepadnaviridae family is characterized by the presence of a circular, partially double stranded DNA molecule. Hepatitis B virus consists of a icosahedral core within a closely adherent capsid that contains cellular lipid, glycoproteins, and a virus-specific surface antigen called Hepatitis B surface antigen (HBsAg). The virus encodes a reverse transcriptase and replicates through an RNA intermediate. Hepatitis B virus shows tropism to the liver and replicates in hepatocytes. Hepatitis B is also called serum hepatitis and is caused by a DNA virus known as hepatitis B virus. It is transmitted by parenteral or sexual routes. Hepatitis B has a longer incubation period, which is approximately 50-160 days. Onset of the disease is gradual and the infection can be acute or self-limiting or can lead to persistent viremia and chronic liver disease with immunologic complications. The Hepatitis A virus is a naked icosahedron that is member of the Picornaviridae family. The genome of this virus is infectious and contains a single linear molecule of single stranded RNA. Hepatitis A is transmitted by feco-oral routes and was known as infectious hepatitis. The virus enters the body by ingestion and multiplies in intestinal epithelial cells. The virus then enters the circulation and invades parenchymal cells in the liver. Incubation period for Hepatitis A is 15-40 days. Hepatitis D virus is a very small virus with tiny genome and is classified under genus Deltavirus. It is defective satellite virus and needs Hepatitis B virus as helper, i.e., it is infective only in the presence of Hepatitis B virus. The outer capsid of the virion contains Hepatitis B surface antigen, which is encoded by HBV co-infecting the same cell. Hepatitis E virus is a naked virus, which has icosahedral capsid with surface depression. Hepatitis E virus is from the family Calciviridae and contains a single molecule of a single stranded RNA. Hepatitis A is transmitted by feco-oral routes and by contaminated food and water. Hepatitis E is associated with cholestasis and has a higher fatality rate in pregnant women. Hepatitis A virus and Hepatitis E virus are not associated with: Parenteral transmission. Chronic carrier state. Chronic hepatitis. Cirrhosis. Hepatocellular carcinoma. Hepatitis B virus, Hepatitis C virus, and Hepatitis D virus are associated with: Parenteral transmission. Chronic carrier state. Chronic hepatitis. Cirrhosis. Hepatocellular carcinoma.

Question 54

Which of the following is a DNA virus that replicates through a circular RNA intermediate and is a member of the Hepadnaviridae family? Answer Choices ## Footnote 1 Hepatitis A virus 2 Hepatitis B virus 3 Hepatitis C virus 4 Hepatitis D virus 5 Hepatitis E virus

Answer 54

Hepatitis B virus ## Footnote Hepatitis C is an enveloped icosahedral RNA virus with gene order characteristic of the family Flaviviridae. The genome of Hepatitis C is infectious and consists of a linear single stranded 9.5 kb molecule of RNA. The virus replicates in the cytoplasm. Hepatitis C is transmitted by paranteral and sexual routes. It is the most common cause of post-transfusion hepatitis. Hepatitis C is associated with acute infection, chronic liver disease, and cirrhosis. Hepatitis C viral infection may serve as a predisposing factor in primary hepatocellular carcinoma. Hepatitis B virus is an enveloped DNA virus that is part of the Hepadnaviridae family. The genome of Hepadnaviridae family is characterized by the presence of a circular, partially double stranded DNA molecule. Hepatitis B virus consists of a icosahedral core within a closely adherent capsid that contains cellular lipid, glycoproteins, and a virus-specific surface antigen called Hepatitis B surface antigen (HBsAg). The virus encodes a reverse transcriptase and replicates through an RNA intermediate. Hepatitis B virus shows tropism to the liver and replicates in hepatocytes. Hepatitis B is also called serum hepatitis and is caused by a DNA virus known as hepatitis B virus. It is transmitted by parenteral or sexual routes. Hepatitis B has a longer incubation period, which is approximately 50-160 days. Onset of the disease is gradual and the infection can be acute or self-limiting or can lead to persistent viremia and chronic liver disease with immunologic complications. The Hepatitis A virus is a naked icosahedron that is member of the Picornaviridae family. The genome of this virus is infectious and contains a single linear molecule of single stranded RNA. Hepatitis A is transmitted by feco-oral routes and was known as infectious hepatitis. The virus enters the body by ingestion and multiplies in intestinal epithelial cells. The virus then enters the circulation and invades parenchymal cells in the liver. Incubation period for Hepatitis A is 15-40 days. Hepatitis D virus is a very small virus with tiny genome and is classified under genus Deltavirus. It is defective satellite virus and needs Hepatitis B virus as helper, i.e., it is infective only in the presence of Hepatitis B virus. The outer capsid of the virion contains Hepatitis B surface antigen, which is encoded by HBV co-infecting the same cell. Hepatitis E virus is a naked virus, which has icosahedral capsid with surface depression. Hepatitis E virus is from the family Calciviridae and contains a single molecule of a single stranded RNA. Hepatitis A is transmitted by feco-oral routes and by contaminated food and water. Hepatitis E is associated with cholestasis and has a higher fatality rate in pregnant women. Hepatitis A virus and Hepatitis E virus are not associated with: Parenteral transmission. Chronic carrier state. Chronic hepatitis. Cirrhosis. Hepatocellular carcinoma. Hepatitis B virus, Hepatitis C virus, and Hepatitis D virus are associated with: Parenteral transmission. Chronic carrier state. Chronic hepatitis. Cirrhosis. Hepatocellular carcinoma.

Question 55

Which of the following is an etiological agent of infectious hepatitis and a member of the Picornaviridae family? ## Footnote 1 Hepatitis A virus 2 Hepatitis B virus 3 Hepatitis C virus 4 Hepatitis D virus 5 Hepatitis E virus

Answer 55

Hepatitis A virus ## Footnote Hepatitis C is an enveloped icosahedral RNA virus with gene order characteristic of the family Flaviviridae. The genome of Hepatitis C is infectious and consists of a linear single stranded 9.5 kb molecule of RNA. The virus replicates in the cytoplasm. Hepatitis C is transmitted by paranteral and sexual routes. It is the most common cause of post-transfusion hepatitis. Hepatitis C is associated with acute infection, chronic liver disease, and cirrhosis. Hepatitis C viral infection may serve as a predisposing factor in primary hepatocellular carcinoma. Hepatitis B virus is an enveloped DNA virus that is part of the Hepadnaviridae family. The genome of Hepadnaviridae family is characterized by the presence of a circular, partially double stranded DNA molecule. Hepatitis B virus consists of a icosahedral core within a closely adherent capsid that contains cellular lipid, glycoproteins, and a virus-specific surface antigen called Hepatitis B surface antigen (HBsAg). The virus encodes a reverse transcriptase and replicates through an RNA intermediate. Hepatitis B virus shows tropism to the liver and replicates in hepatocytes. Hepatitis B is also called serum hepatitis and is caused by a DNA virus known as hepatitis B virus. It is transmitted by parenteral or sexual routes. Hepatitis B has a longer incubation period, which is approximately 50-160 days. Onset of the disease is gradual and the infection can be acute or self-limiting or can lead to persistent viremia and chronic liver disease with immunologic complications. The Hepatitis A virus is a naked icosahedron that is member of the Picornaviridae family. The genome of this virus is infectious and contains a single linear molecule of single stranded RNA. Hepatitis A is transmitted by feco-oral routes and was known as infectious hepatitis. The virus enters the body by ingestion and multiplies in intestinal epithelial cells. The virus then enters the circulation and invades parenchymal cells in the liver. Incubation period for Hepatitis A is 15-40 days. Hepatitis D virus is a very small virus with tiny genome and is classified under genus Deltavirus. It is defective satellite virus and needs Hepatitis B virus as helper, i.e., it is infective only in the presence of Hepatitis B virus. The outer capsid of the virion contains Hepatitis B surface antigen, which is encoded by HBV co-infecting the same cell. Hepatitis E virus is a naked virus, which has icosahedral capsid with surface depression. Hepatitis E virus is from the family Calciviridae and contains a single molecule of a single stranded RNA. Hepatitis A is transmitted by feco-oral routes and by contaminated food and water. Hepatitis E is associated with cholestasis and has a higher fatality rate in pregnant women. Hepatitis A virus and Hepatitis E virus are not associated with: Parenteral transmission. Chronic carrier state. Chronic hepatitis. Cirrhosis. Hepatocellular carcinoma. Hepatitis B virus, Hepatitis C virus, and Hepatitis D virus are associated with: Parenteral transmission. Chronic carrier state. Chronic hepatitis. Cirrhosis. Hepatocellular carcinoma.

Question 56

Which of the following is a non-enveloped RNA virus from the family Calciviridae that is associated with cholestasis? ## Footnote 1 Hepatitis A virus 2 Hepatitis B virus 3 Hepatitis C virus 4 Hepatitis D virus 5 Hepatitis E virus

Answer 56

Hepatitis E virus ## Footnote Hepatitis C is an enveloped icosahedral RNA virus with gene order characteristic of the family Flaviviridae. The genome of Hepatitis C is infectious and consists of a linear single stranded 9.5 kb molecule of RNA. The virus replicates in the cytoplasm. Hepatitis C is transmitted by paranteral and sexual routes. It is the most common cause of post-transfusion hepatitis. Hepatitis C is associated with acute infection, chronic liver disease, and cirrhosis. Hepatitis C viral infection may serve as a predisposing factor in primary hepatocellular carcinoma. Hepatitis B virus is an enveloped DNA virus that is part of the Hepadnaviridae family. The genome of Hepadnaviridae family is characterized by the presence of a circular, partially double stranded DNA molecule. Hepatitis B virus consists of a icosahedral core within a closely adherent capsid that contains cellular lipid, glycoproteins, and a virus-specific surface antigen called Hepatitis B surface antigen (HBsAg). The virus encodes a reverse transcriptase and replicates through an RNA intermediate. Hepatitis B virus shows tropism to the liver and replicates in hepatocytes. Hepatitis B is also called serum hepatitis and is caused by a DNA virus known as hepatitis B virus. It is transmitted by parenteral or sexual routes. Hepatitis B has a longer incubation period, which is approximately 50-160 days. Onset of the disease is gradual and the infection can be acute or self-limiting or can lead to persistent viremia and chronic liver disease with immunologic complications. The Hepatitis A virus is a naked icosahedron that is member of the Picornaviridae family. The genome of this virus is infectious and contains a single linear molecule of single stranded RNA. Hepatitis A is transmitted by feco-oral routes and was known as infectious hepatitis. The virus enters the body by ingestion and multiplies in intestinal epithelial cells. The virus then enters the circulation and invades parenchymal cells in the liver. Incubation period for Hepatitis A is 15-40 days. Hepatitis D virus is a very small virus with tiny genome and is classified under genus Deltavirus. It is defective satellite virus and needs Hepatitis B virus as helper, i.e., it is infective only in the presence of Hepatitis B virus. The outer capsid of the virion contains Hepatitis B surface antigen, which is encoded by HBV co-infecting the same cell. Hepatitis E virus is a naked virus, which has icosahedral capsid with surface depression. Hepatitis E virus is placed in a sole genus Hepevirus, within a new family Hepeviridae, and contains a single molecule of a single stranded RNA. Hepatitis A is transmitted by feco-oral routes and by contaminated food and water. Hepatitis E is associated with cholestasis and has a higher fatality rate in pregnant women. Hepatitis A virus and Hepatitis E virus are not associated with: Parenteral transmission. Chronic carrier state. Chronic hepatitis. Cirrhosis. Hepatocellular carcinoma. Hepatitis B virus, Hepatitis C virus, and Hepatitis D virus are associated with: Parenteral transmission. Chronic carrier state. Chronic hepatitis. Cirrhosis. Hepatocellular carcinoma.

Question 57

Which of the following is a Deltavirus which is infective only in the presence of the hepatitis B virus? ## Footnote 1 Hepatitis A virus 2 Hepatitis B virus 3 Hepatitis C virus 4 Hepatitis D virus 5 Hepatitis E virus

Answer 57

Hepatitis D virus ## Footnote Hepatitis C is an enveloped icosahedral RNA virus with gene order characteristic of the family Flaviviridae. The genome of Hepatitis C is infectious and consists of a linear single stranded 9.5 kb molecule of RNA. The virus replicates in the cytoplasm. Hepatitis C is transmitted by paranteral and sexual routes. It is the most common cause of post-transfusion hepatitis. Hepatitis C is associated with acute infection, chronic liver disease, and cirrhosis. Hepatitis C viral infection may serve as a predisposing factor in primary hepatocellular carcinoma. Hepatitis B virus is an enveloped DNA virus that is part of the Hepadnaviridae family. The genome of Hepadnaviridae family is characterized by the presence of a circular, partially double stranded DNA molecule. Hepatitis B virus consists of a icosahedral core within a closely adherent capsid that contains cellular lipid, glycoproteins, and a virus-specific surface antigen called Hepatitis B surface antigen (HBsAg). The virus encodes a reverse transcriptase and replicates through an RNA intermediate. Hepatitis B virus shows tropism to the liver and replicates in hepatocytes. Hepatitis B is also called serum hepatitis and is caused by a DNA virus known as hepatitis B virus. It is transmitted by parenteral or sexual routes. Hepatitis B has a longer incubation period, which is approximately 50-160 days. Onset of the disease is gradual and the infection can be acute or self-limiting or can lead to persistent viremia and chronic liver disease with immunologic complications. The Hepatitis A virus is a naked icosahedron that is member of the Picornaviridae family. The genome of this virus is infectious and contains a single linear molecule of single stranded RNA. Hepatitis A is transmitted by feco-oral routes and was known as infectious hepatitis. The virus enters the body by ingestion and multiplies in intestinal epithelial cells. The virus then enters the circulation and invades parenchymal cells in the liver. Incubation period for Hepatitis A is 15-40 days. Hepatitis D virus is a very small virus with tiny genome and is classified under genus Deltavirus. It is defective satellite virus and needs Hepatitis B virus as helper, i.e., it is infective only in the presence of Hepatitis B virus. The outer capsid of the virion contains Hepatitis B surface antigen, which is encoded by HBV co-infecting the same cell. Hepatitis E virus is a naked virus, which has icosahedral capsid with surface depression. Hepatitis E virus is from the family Calciviridae and contains a single molecule of a single stranded RNA. Hepatitis A is transmitted by feco-oral routes and by contaminated food and water. Hepatitis E is associated with cholestasis and has a higher fatality rate in pregnant women. Hepatitis A virus and Hepatitis E virus are not associated with: Parenteral transmission. Chronic carrier state. Chronic hepatitis. Cirrhosis. Hepatocellular carcinoma. Hepatitis B virus, Hepatitis C virus, and Hepatitis D virus are associated with: Parenteral transmission. Chronic carrier state. Chronic hepatitis. Cirrhosis. Hepatocellular carcinoma.

Question 58

Reactivation of varicella zoster virus can be manifested as ## Footnote 1 Chickenpox 2 Glandular fever 3 Shingles 4 Cold sore 5 Burkitt's lymphoma

Answer 58

Shingles ## Footnote Initial episode of infection with varicella zoster virus is manifested as chickenpox and generally occurs in childhood. The virus can remain dormant in the dorsal root ganglia for years. Shingles (Herpes zoster) is the reactivation of the varicella zoster virus and occurs in the elderly who had chickenpox in childhood. Shingles is triggered by declining immunity to the virus and is characterized by a rash that is mostly limited largely to an area of skin innervated by a single sensory ganglion. The skin lesion is more painful and generally occurs with recurrent herpes simplex. Epstein-Barr virus is implicated in Glandular fever and Burkitt's lymphoma. Reactivation of herpes simplex 1 virus can cause cold sore.

Question 59

What viral inclusion corresponds with the rabies virus? ## Footnote 1 Owl's eye-intranuclear basophilic inclusion body in cells of tissues or urine sediment 2 Negri bodies (intracytoplasmic) in brain tissue 3 Cowdry Type A intranuclear inclusion body in single cells or in large syncytia 4 Guarnieri bodies in the cytoplasm of infected cells 5 Perinuclear acidophilic inclusion body in the cytoplasm

Answer 59

Negri bodies (intracytoplasmic) in brain tissue ## Footnote The inclusion bodies are the stainable structures found within the nucleus or cytoplasm of the host cell. Inclusion bodies result from the histological changes caused by the presence of viral components or the changes in the cell structure mediated by the infecting virus. The detection of the inclusion bodies by microscopic examination can be used for laboratory diagnosis of the viral infection, as they are characteristic for particular viral infections. Negri bodies are acidophilic inclusions found in the cytoplasm in brain tissue and are characteristic of infection with the rabies virus. Cowdry Type A inclusions are intranuclear inclusion bodies characteristic of infection with varicella zoster virus (VZV) or herpes simplex virus (HSV). These inclusions can be found in single cells or in large syncytia. Examination of the HSV infected cells in tissues or smear reveals giant cells with characteristic intranuclear inclusions that are acidophilic and are known as Cowdry Type A inclusions. Cowdry Type A inclusions are also seen in skin lesions, respiratory specimens, or organ biopsies in the cytological examination of cells infected with VZV. Owl's eye-intranuclear inclusions are characteristic of cytomegalovirus infection. These are large basophilic inclusion bodies detected in cells of tissues or urine sediment stained for cytological examination. Guarnieri bodies are inclusion bodies, associated with infection with the pox virus. The scraping of cells from the lesion is stained and examined microscopically. Guarnieri bodies appear as acidophilic inclusions in the cytoplasm of infected cells. Perinuclear inclusion bodies in the cytoplasm are associated with reovirus infection. When the infected cells are observed for cytopathic effect, the inclusions appear as small dots in the periphery of the host cell cytoplasm early in the infectious cycle. Larger acidophilic inclusions located adjacent to the nucleus are detected later in the infectious cycle.

Question 60

Which of the following viral inclusions correspond with the varicella-zoster virus (VZV)? ## Footnote 1 Owl's eye-intranuclear basophilic inclusion body in cells of tissues or urine sediment 2 Negri bodies (intracytoplasmic) in brain tissue 3 Cowdry Type A intranuclear inclusion body in single cells or in large syncytia 4 Guarnieri bodies in the cytoplasm of infected cells 5 Perinuclear acidophilic inclusion body in the cytoplasm

Answer 60

Cowdry Type A intranuclear inclusion body in single cells or in large syncytia ## Footnote The inclusion bodies are the stainable structures found within the nucleus or cytoplasm of the host cell. Inclusion bodies result from the histological changes caused by the presence of viral components, or the changes in the cell structure mediated by the infecting virus. The detection of the inclusion bodies by microscopic examination can be used for laboratory diagnosis of the viral infection, as they are characteristic for particular viral infections. Cowdry Type A inclusions are intranuclear inclusion bodies characteristic of infection with varicella zoster virus (VZV) or herpes simplex virus(HSV). These inclusions can be found in single cells, or in large syncytia. Examination of the HSV infected cells in tissues, or smear, reveals giant cells with characteristic intranuclear inclusions that are acidophilic and are known as Cowdry Type A inclusions. Cowdry Type A inclusions are also seen in skin lesions, respiratory specimens, or organ biopsies in the cytological examination of cells infected with VZV. Negri bodies are acidophilic inclusions found in the cytoplasm in brain tissue and are characteristic of infection with the rabies virus. Owl's eye-intranuclear inclusions are characteristic of cytomegalovirus infection. These are large basophilic inclusion bodies detected in cells of tissues or urine sediment stained for cytological examination. Guarnieri bodies are inclusion bodies, associated with infection with the pox virus. The scraping of cells from the lesion is stained and examined microscopically. Guarnieri bodies appear as acidophilic inclusions in the cytoplasm of infected cells. Perinuclear inclusion bodies in the cytoplasm are associated with reovirus infection. When the infected cells are observed for cytopathic effect, early in the infectious cycle, the inclusions appear as small dots in the periphery of the host cell cytoplasm. Larger acidophilic inclusions located adjacent to the nucleus are detected later in the infectious cycle.

Question 61

Which of the following viral inclusions correspond with the herpes simplex virus? ## Footnote 1 Owl's eye-intranuclear basophilic inclusion body in cells of tissues or urine sediment 2 Negri bodies (intracytoplasmic) in brain tissue 3 Cowdry Type A intranuclear inclusion body in single cells or in large syncytia 4 Guarnieri bodies in the cytoplasm of infected cells 5 Perinuclear acidophilic inclusion body in the cytoplasm

Answer 61

Cowdry Type A intranuclear inclusion body in single cells or in large syncytia ## Footnote The inclusion bodies are the stainable structures found within the nucleus or cytoplasm of the host cell. Inclusion bodies result from the histological changes caused by the presence of viral components or the changes in the cell structure mediated by the infecting virus. The detection of the inclusion bodies by microscopic examination can be used for laboratory diagnosis of the viral infection, as they are characteristic for particular viral infections. Negri bodies are acidophilic inclusions found in the cytoplasm in brain tissue and are characteristic of infection with the rabies virus. Cowdry Type A inclusions are intranuclear inclusion bodies characteristic of infection with varicella zoster virus (VZV) or herpes simplex virus (HSV). These inclusions can be found in single cells or in large syncytia. Examination of the HSV infected cells in tissues or smear reveals giant cells with characteristic intranuclear inclusions that are acidophilic and are known as Cowdry Type A inclusions. Cowdry Type A inclusions are also seen in skin lesions, respiratory specimens, or organ biopsies in the cytological examination of cells infected with VZV. Owl's eye-intranuclear inclusions are characteristic of cytomegalovirus infection. These are large basophilic inclusion bodies detected in cells of tissues or urine sediment stained for cytological examination. Guarnieri bodies are inclusion bodies, associated with infection with the pox virus. The scraping of cells from the lesion is stained and examined microscopically. Guarnieri bodies appear as acidophilic inclusions in the cytoplasm of infected cells. Perinuclear inclusion bodies in the cytoplasm are associated with reovirus infection. When the infected cells are observed for cytopathic effect, the inclusions appear as small dots in the periphery of the host cell cytoplasm early in the infectious cycle. Larger acidophilic inclusions located adjacent to the nucleus are detected later in the infectious cycle.

Question 62

Which of the following viral inclusions correspond with the cytomegalovirus? ## Footnote 1 Owl's eye-intranuclear basophilic inclusion body in cells of tissues or urine sediment. 2 Negri bodies (intracytoplasmic) in brain tissue. 3 Cowdry Type A intranuclear inclusion body in single cells or in large syncytia. 4 Guarnieri bodies in the cytoplasm of infected cells. 5 Perinuclear acidophilic inclusion body in the cytoplasm.

Answer 62

Owl's eye-intranuclear basophilic inclusion body in cells of tissues or urine sediment. ## Footnote The inclusion bodies are the stainable structures found within the nucleus or cytoplasm of the host cell. Inclusion bodies result from the histological changes caused by the presence of viral components or the changes in the cell structure mediated by the infecting virus. The detection of the inclusion bodies by microscopic examination can be used for laboratory diagnosis of the viral infection, as they are characteristic for particular viral infections. Negri bodies are acidophilic inclusions found in the cytoplasm in brain tissue and are characteristic of infection with the rabies virus. Cowdry Type A inclusions are intranuclear inclusion bodies characteristic of infection with varicella zoster virus (VZV) or herpes simplex virus (HSV). These inclusions can be found in single cells or in large syncytia. Examination of the HSV infected cells in tissues or smear reveals giant cells with characteristic intranuclear inclusions that are acidophilic and are known as Cowdry Type A inclusions. Cowdry Type A inclusions are also seen in skin lesions, respiratory specimens, or organ biopsies in the cytological examination of cells infected with VZV. Owl's eye-intranuclear inclusions are characteristic of cytomegalovirus infection. These are large basophilic inclusion bodies detected in cells of tissues or urine sediment stained for cytological examination. Guarnieri bodies are inclusion bodies, associated with infection with the pox virus. The scraping of cells from the lesion is stained and examined microscopically. Guarnieri bodies appear as acidophilic inclusions in the cytoplasm of infected cells. Perinuclear inclusion bodies in the cytoplasm are associated with reovirus infection. When the infected cells are observed for cytopathic effect, the inclusions appear as small dots in the periphery of the host cell cytoplasm early in the infectious cycle. Larger acidophilic inclusions located adjacent to the nucleus are detected later in the infectious cycle.

Question 63

Which of the following viral inclusions correspond with the pox virus? ## Footnote 1 Owl's eye-intranuclear basophilic inclusion body in cells of tissues or urine sediment 2 Negri bodies (intracytoplasmic) in brain tissue 3 Cowdry Type A intranuclear inclusion body in single cells or in large syncytia 4 Guarnieri bodies in the cytoplasm of infected cells 5 Perinuclear acidophilic inclusion body in the cytoplasm

Answer 63

Guarnieri bodies in the cytoplasm of infected cells ## Footnote The inclusion bodies are the stainable structures found within the nucleus or cytoplasm of the host cell. Inclusion bodies result from the histological changes caused by the presence of viral components or the changes in the cell structure mediated by the infecting virus. The detection of the inclusion bodies by microscopic examination can be used for laboratory diagnosis of the viral infection, as they are characteristic for particular viral infections. Negri bodies are acidophilic inclusions found in the cytoplasm in brain tissue and are characteristic of infection with the rabies virus. Cowdry Type A inclusions are intranuclear inclusion bodies characteristic of infection with varicella zoster virus (VZV) or herpes simplex virus (HSV). These inclusions can be found in single cells or in large syncytia. Examination of the HSV infected cells in tissues or smear reveals giant cells with characteristic intranuclear inclusions that are acidophilic and are known as Cowdry Type A inclusions. Cowdry Type A inclusions are also seen in skin lesions, respiratory specimens, or organ biopsies in the cytological examination of cells infected with VZV. Owl's eye-intranuclear inclusions are characteristic of cytomegalovirus infection. These are large basophilic inclusion bodies detected in cells of tissues or urine sediment stained for cytological examination. Guarnieri bodies are inclusion bodies, associated with infection with the pox virus. The scraping of cells from the lesion is stained and examined microscopically. Guarnieri bodies appear as acidophilic inclusions in the cytoplasm of infected cells. Perinuclear inclusion bodies in the cytoplasm are associated with reovirus infection. When the infected cells are observed for cytopathic effect, the inclusions appear as small dots in the periphery of the host cell cytoplasm early in the infectious cycle. Larger acidophilic inclusions located adjacent to the nucleus are detected later in the infectious cycle.

Question 64

Which of the following viral inclusions correspond with the reovirus ## Footnote 1 Owl's eye-intranuclear basophilic inclusion body in cells of tissues or urine sediment 2 Negri bodies (intracytoplasmic) in brain tissue 3 Cowdry Type A intranuclear inclusion body in single cells or in large syncytia 4 Guarnieri bodies in the cytoplasm of infected cells 5 Perinuclear acidophilic inclusion body in the cytoplasm

Answer 64

Perinuclear acidophilic inclusion body in the cytoplasm ## Footnote The inclusion bodies are the stainable structures found within the nucleus or cytoplasm of the host cell. Inclusion bodies result from the histological changes caused by the presence of viral components or the changes in the cell structure mediated by the infecting virus. The detection of the inclusion bodies by microscopic examination can be used for laboratory diagnosis of the viral infection, as they are characteristic for particular viral infections. Negri bodies are acidophilic inclusions found in the cytoplasm in brain tissue and are characteristic of infection with the rabies virus. Cowdry Type A inclusions are intranuclear inclusion bodies characteristic of infection with varicella zoster virus (VZV) or herpes simplex virus (HSV). These inclusions can be found in single cells or in large syncytia. Examination of the HSV infected cells in tissues or smear reveals giant cells with characteristic intranuclear inclusions that are acidophilic and are known as Cowdry Type A inclusions. Cowdry Type A inclusions are also seen in skin lesions, respiratory specimens, or organ biopsies in the cytological examination of cells infected with VZV. Owl's eye-intranuclear inclusions are characteristic of cytomegalovirus infection. These are large basophilic inclusion bodies detected in cells of tissues or urine sediment stained for cytological examination. Guarnieri bodies are inclusion bodies, associated with infection with the pox virus. The scraping of cells from the lesion is stained and examined microscopically. Guarnieri bodies appear as acidophilic inclusions in the cytoplasm of infected cells. Perinuclear inclusion bodies in the cytoplasm are associated with reovirus infection. When the infected cells are observed for cytopathic effect, the inclusions appear as small dots in the periphery of the host cell cytoplasm early in the infectious cycle. Larger acidophilic inclusions located adjacent to the nucleus are detected later in the infectious cycle.

Question 65

What clinical condition is associated with the human papilloma virus? ## Footnote 1 Hepatocellular carcinoma 2 Cervical cancer 3 Herpangina 4 Bone break fever 5 Gingivostomatitis

Answer 65

Cervical cancer ## Footnote The majority of cervical cancers (approximately 90%) contain human papilloma virus DNA, usually of type 16 or 18. Human papilloma viruses are members of the family Papovaviridae and have predilection for the skin and mucous membranes. Human papilloma viruses are associated with warts, respiratory papillomas, oral infections, and genital infections. Human papilloma viral infection may progress over a period of years through the various stages of cervical intraepithelial neoplasia to invasive squamous carcinoma. Hepatitis B virus (HBV) is a human carcinogen associated with hepatocellular carcinoma. The incidence of hepatocellular carcinoma is higher in a person who becomes infected with HBV earlier in life. The pattern observed is: person develops chronic hepatitis leading to cirrhosis of the liver and eventually to liver cancer 20-50 years post-infection. The genome of HBV is small and comprises a small, circular, partially double-stranded DNA molecule. HBV replicates in hepatocyte and involves RNA intermediate and a virus coded reverse transcriptase. HBV can become integrated into the cellular chromosome during chronic infection, and it may promote genetic instability in the cell. Dengue fever virus and Powassan virus are members of the family Flaviviridae. Flaviviruses are enveloped viruses with icosahedral symmetry. The genome consists of a linear single-stranded RNA molecule, and replication occurs in the cytoplasm. Dengue fever virus is transmitted by the mosquito and is associated with bone break fever and dengue shock syndrome. Bone break fever is characterized by headache, myalgia, arthralgia, and rash. Secondary exposure can result in dengue shock syndrome, and it is characterized by gastrointestinal hemorrhage. Herpes simplex virus type 1 (HSV-1) is a member of the Herpesviridae family and consists of a double-stranded DNA genome. Primary infection with HSV-1 mostly involves the mouth and/or throat. Gingivostomatitis is a classic clinical presentation of HSV-1 infection. It is characterized by formation of vesicles on the mouth and gums, which rupture to become ulcers. Coxsackievirus type A and coxsackievirus type B are members of the Picornaviridae family. Picornaviruses are naked viruses with an icosahedral nucleocapsid. The genome consists of single molecule of single stranded RNA. Coxsackievirus type A is associated with herpangina, which is commonly seen in children. Herpangina is a severe febrile pharyngitis characterized by vesicles or nodules primarily on the soft palate.

Question 66

Which of the following clinical conditions is associated with the hepatitis B virus? ## Footnote 1 Hepatocellular carcinoma 2 Cervical cancer 3 Herpangia 4 Bone break fever 5 Gingivostomatitis 6 Tick-borne encephalitis 7 Smallpox 8 Bornholm disease

Answer 66

Hepatocellular carcinoma ## Footnote Majority of cervical cancers (approximately 90%) contain human papilloma virus DNA, usually of type 16 or 18. Human papilloma viruses are members of the family Papovaviridae and have predilection for the skin and mucous membranes. Human papilloma viruses are associated with warts, respiratory papillomas, oral infections, and genital infections. Human papilloma viral infection may progress over a period of years through the various stages of cervical intraepithelial neoplasia to invasive squamous carcinoma. Hepatitis B virus (HBV) is a human carcinogen associated with hepatocellular carcinoma. The incidence of hepatocellular carcinoma is higher in a person who becomes infected with HBV earlier in life. The pattern observed is: person develops chronic hepatitis leading to cirrhosis of the liver and eventually to liver cancer 20-50 years post-infection. The genome of HBV is small and comprises a small, circular, partially double stranded DNA molecule. HBV replicates in hepatocyte and involves RNA intermediate and a virus coded reverse transcriptase. HBV can become integrated into the cellular chromosome during chronic infection and may promote genetic instability in the cell. Dengue fever virus and Powassan virus are members of the family Flaviviridae. Flaviviruses are enveloped viruses with icosahedral symmetry. The genome consists of a linear single stranded RNA molecule and replication occurs in the cytoplasm. Dengue fever virus is transmitted by the mosquito and is associated with bone break fever and dengue shock syndrome. Bone break fever is characterized by headache, myalgia, arthralgia, and rash. Secondary exposure can result in dengue shock syndrome and is characterized by gastrointestinal hemorrhage. Powassan virus is associated with tick-borne virus encephalitis. Ixodes tick is the vector for Powassan virus. Domestic animals can play a role in the spread of the disease, as the tick can bite the domestic and farm animals and humans can be infected by the ingestion of raw milk or tick bite. Herpes simplex virus type 1 (HSV-1) is a member of the Herpesviridae family and consists of a double stranded DNA genome. Primary infection with HSV-1 mostly involves the mouth and/or throat. Gingivostomatitis is a classic clinical presentation of HSV-1 infection. It is characterized by formation of vesicles on the mouth and gums, which rupture to become ulcers. Coxsackievirus type A and coxsackievirus type B are members of the Picornaviridae family. Picornaviruses are naked viruses with an icosahedral nucleocapsid. The genome consists of single molecule of single stranded RNA. Coxsackievirus type A is associated with herpangina, which is commonly seen in children. Herpangina is a severe febrile pharyngitis characterized by vesicles or nodules primarily on the soft palate. Coxsackievirus type B is associated with Bornholm disease seen mainly in older children and young adults. Bornholm disease is myositis and is also called Pleurodynia. It is characterized by paroxysms of stabbing pain in the chest muscles and abdomen muscles. Variola virus is a brick-shaped virus with a single linear molecule of double stranded DNA and is a member of the Poxviridae family. Variola virus was the causative agent of smallpox that multiplied in the lymph nodes. Smallpox is an ancient disease that is eradicated.

Question 67

Which of the following clinical conditions is associated with the Dengue fever virus? ## Footnote 1 Hepatocellular carcinoma 2 Cervical cancer 3 Herpangia 4 Bone break fever 5 Gingivostomatitis 6 Tick-borne encephalitis 7 Smallpox 8 Bornholm disease

Answer 67

Bone break fever ## Footnote Majority of cervical cancers (approximately 90%) contain human papilloma virus DNA, usually of type 16 or 18. Human papilloma viruses are members of the family Papovaviridae and have predilection for the skin and mucous membranes. Human papilloma viruses are associated with warts, respiratory papillomas, oral infections, and genital infections. Human papilloma viral infection may progress over a period of years through the various stages of cervical intraepithelial neoplasia to invasive squamous carcinoma. Hepatitis B virus (HBV) is a human carcinogen associated with hepatocellular carcinoma. The incidence of hepatocellular carcinoma is higher in a person who becomes infected with HBV earlier in life. The pattern observed is: person develops chronic hepatitis leading to cirrhosis of the liver and eventually to liver cancer 20-50 years post-infection. The genome of HBV is small and comprises a small, circular, partially double stranded DNA molecule. HBV replicates in hepatocyte and involves RNA intermediate and a virus coded reverse transcriptase. HBV can become integrated into the cellular chromosome during chronic infection and may promote genetic instability in the cell. Dengue fever virus and Powassan virus are members of the family Flaviviridae. Flaviviruses are enveloped viruses with icosahedral symmetry. The genome consists of a linear single stranded RNA molecule and replication occurs in the cytoplasm. Dengue fever virus is transmitted by the mosquito and is associated with bone break fever and dengue shock syndrome. Bone break fever is characterized by headache, myalgia, arthralgia, and rash. Secondary exposure can result in dengue shock syndrome and is characterized by gastrointestinal hemorrhage. Powassan virus is associated with tick-borne virus encephalitis. Ixodes tick is the vector for Powassan virus. Domestic animals can play a role in the spread of the disease, as the tick can bite the domestic and farm animals and humans can be infected by the ingestion of raw milk or tick bite. Herpes simplex virus type 1 (HSV-1) is a member of the Herpesviridae family and consists of a double stranded DNA genome. Primary infection with HSV-1 mostly involves the mouth and/or throat. Gingivostomatitis is a classic clinical presentation of HSV-1 infection. It is characterized by formation of vesicles on the mouth and gums, which rupture to become ulcers. Coxsackievirus type A and coxsackievirus type B are members of the Picornaviridae family. Picornaviruses are naked viruses with an icosahedral nucleocapsid. The genome consists of single molecule of single stranded RNA. Coxsackievirus type A is associated with herpangina, which is commonly seen in children. Herpangina is a severe febrile pharyngitis characterized by vesicles or nodules primarily on the soft palate. Coxsackievirus type B is associated with Bornholm disease seen mainly in older children and young adults. Bornholm disease is myositis and is also called Pleurodynia. It is characterized by paroxysms of stabbing pain in the chest muscles and abdomen muscles. Variola virus is a brick-shaped virus with a single linear molecule of double stranded DNA and is a member of the Poxviridae family. Variola virus was the causative agent of smallpox that multiplied in the lymph nodes. Smallpox is an ancient disease that is eradicated.

Question 68

Which of the following clinical conditions is associated with the Powassan virus? ## Footnote 1 Hepatocellular carcinoma 2 Cervical cancer 3 Herpangia 4 Bone break fever 5 Gingivostomatitis 6 Tick-borne encephalitis 7 Smallpox 8 Bornholm disease

Answer 68

Tick-borne encephalitis ## Footnote Majority of cervical cancers (approximately 90%) contain human papilloma virus DNA, usually of type 16 or 18. Human papilloma viruses are members of the family Papovaviridae and have predilection for the skin and mucous membranes. Human papilloma viruses are associated with warts, respiratory papillomas, oral infections, and genital infections. Human papilloma viral infection may progress over a period of years through the various stages of cervical intraepithelial neoplasia to invasive squamous carcinoma. Hepatitis B virus (HBV) is a human carcinogen associated with hepatocellular carcinoma. The incidence of hepatocellular carcinoma is higher in a person who becomes infected with HBV earlier in life. The pattern observed is: person develops chronic hepatitis leading to cirrhosis of the liver and eventually to liver cancer 20-50 years post-infection. The genome of HBV is small and comprises a small, circular, partially double stranded DNA molecule. HBV replicates in hepatocyte and involves RNA intermediate and a virus coded reverse transcriptase. HBV can become integrated into the cellular chromosome during chronic infection and may promote genetic instability in the cell. Dengue fever virus and Powassan virus are members of the family Flaviviridae. Flaviviruses are enveloped viruses with icosahedral symmetry. The genome consists of a linear single stranded RNA molecule and replication occurs in the cytoplasm. Dengue fever virus is transmitted by the mosquito and is associated with bone break fever and dengue shock syndrome. Bone break fever is characterized by headache, myalgia, arthralgia, and rash. Secondary exposure can result in dengue shock syndrome and is characterized by gastrointestinal hemorrhage. Powassan virus is associated with tick-borne virus encephalitis. Ixodes tick is the vector for Powassan virus. Domestic animals can play a role in the spread of the disease, as the tick can bite the domestic and farm animals and humans can be infected by the ingestion of raw milk or tick bite. Herpes simplex virus type 1 (HSV-1) is a member of the Herpesviridae family and consists of a double stranded DNA genome. Primary infection with HSV-1 mostly involves the mouth and/or throat. Gingivostomatitis is a classic clinical presentation of HSV-1 infection. It is characterized by formation of vesicles on the mouth and gums, which rupture to become ulcers. Coxsackievirus type A and coxsackievirus type B are members of the Picornaviridae family. Picornaviruses are naked viruses with an icosahedral nucleocapsid. The genome consists of single molecule of single stranded RNA. Coxsackievirus type A is associated with herpangina, which is commonly seen in children. Herpangina is a severe febrile pharyngitis characterized by vesicles or nodules primarily on the soft palate. Coxsackievirus type B is associated with Bornholm disease seen mainly in older children and young adults. Bornholm disease is myositis and is also called Pleurodynia. It is characterized by paroxysms of stabbing pain in the chest muscles and abdomen muscles. Variola virus is a brick-shaped virus with a single linear molecule of double stranded DNA and is a member of the Poxviridae family. Variola virus was the causative agent of smallpox that multiplied in the lymph nodes. Smallpox is an ancient disease that is eradicated.

Question 69

Which of the following clinical conditions is associated with the herpes simplex virus type 1? ## Footnote 1 Hepatocellular carcinoma 2 Cervical cancer 3 Herpangia 4 Bone break fever 5 Gingivostomatitis 6 Tick-borne encephalitis 7 Smallpox 8 Bornholm disease

Answer 69

Gingivostomatitis ## Footnote Majority of cervical cancers (approximately 90%) contain human papilloma virus DNA, usually of type 16 or 18. Human papilloma viruses are members of the family Papovaviridae and have predilection for the skin and mucous membranes. Human papilloma viruses are associated with warts, respiratory papillomas, oral infections, and genital infections. Human papilloma viral infection may progress over a period of years through the various stages of cervical intraepithelial neoplasia to invasive squamous carcinoma. Hepatitis B virus (HBV) is a human carcinogen associated with hepatocellular carcinoma. The incidence of hepatocellular carcinoma is higher in a person who becomes infected with HBV earlier in life. The pattern observed is: person develops chronic hepatitis leading to cirrhosis of the liver and eventually to liver cancer 20-50 years post-infection. The genome of HBV is small and comprises a small, circular, partially double stranded DNA molecule. HBV replicates in hepatocyte and involves RNA intermediate and a virus coded reverse transcriptase. HBV can become integrated into the cellular chromosome during chronic infection and may promote genetic instability in the cell. Dengue fever virus and Powassan virus are members of the family Flaviviridae. Flaviviruses are enveloped viruses with icosahedral symmetry. The genome consists of a linear single stranded RNA molecule and replication occurs in the cytoplasm. Dengue fever virus is transmitted by the mosquito and is associated with bone break fever and dengue shock syndrome. Bone break fever is characterized by headache, myalgia, arthralgia, and rash. Secondary exposure can result in dengue shock syndrome and is characterized by gastrointestinal hemorrhage. Powassan virus is associated with tick-borne virus encephalitis. Ixodes tick is the vector for Powassan virus. Domestic animals can play a role in the spread of the disease, as the tick can bite the domestic and farm animals and humans can be infected by the ingestion of raw milk or tick bite. Herpes simplex virus type 1 (HSV-1) is a member of the Herpesviridae family and consists of a double stranded DNA genome. Primary infection with HSV-1 mostly involves the mouth and/or throat. Gingivostomatitis is a classic clinical presentation of HSV-1 infection. It is characterized by formation of vesicles on the mouth and gums, which rupture to become ulcers. Coxsackievirus type A and coxsackievirus type B are members of the Picornaviridae family. Picornaviruses are naked viruses with an icosahedral nucleocapsid. The genome consists of single molecule of single stranded RNA. Coxsackievirus type A is associated with herpangina, which is commonly seen in children. Herpangina is a severe febrile pharyngitis characterized by vesicles or nodules primarily on the soft palate. Coxsackievirus type B is associated with Bornholm disease seen mainly in older children and young adults. Bornholm disease is myositis and is also called Pleurodynia. It is characterized by paroxysms of stabbing pain in the chest muscles and abdomen muscles. Variola virus is a brick-shaped virus with a single linear molecule of double stranded DNA and is a member of the Poxviridae family. Variola virus was the causative agent of smallpox that multiplied in the lymph nodes. Smallpox is an ancient disease that is eradicated.

Question 70

Which of the following clinical conditions is associated with the Coxsackievirus type A? ## Footnote 1 Hepatocellular carcinoma 2 Cervical cancer 3 Herpangina 4 Bone break fever 5 Gingivostomatitis 6 Tick-borne encephalitis 7 Smallpox 8 Bornholm disease

Answer 70

Herpangina ## Footnote Coxsackievirus type A and coxsackievirus type B are members of the Picornaviridae family. Coxsackievirus type A is associated with herpangina,which is commonly seen in children. Herpangina is a severe febrile pharyngitis characterized by vesicles or nodules primarily on the soft palate. Coxsackievirus type B is associated with Bornholm disease seen mainly in older children and young adults. Bornholm disease is myositis and is also called Pleurodynia. The majority of cervical cancers (approximately 90%) contain human papilloma virus DNA, usually of type 16 or 18. Hepatitis B virus (HBV) is a human carcinogen associated with hepatocellular carcinoma. The incidence of hepatocellular carcinoma is higher in a person who becomes infected with HBV earlier in life. Dengue fever virus and Powassan virus are members of the family Flaviviridae. Dengue fever virus is transmitted by the mosquito and is associated with bone break fever and dengue shock syndrome. Bone break fever is characterized by headache, myalgia, arthralgia, and rash. Powassan virus is associated with tick-borne virus encephalitis. Ixodes tick is the vector for Powassan virus. Domestic animals can play a role in the spread of the disease. Herpes simplex virus type 1 (HSV-1) is a member of the Herpes viridae family and consists of a double stranded DNA genome. Primary infection with HSV-1 mostly involves the mouth and/or throat. Gingivostomatitis is a classic clinical presentation of HSV-1 infection. Variola virus is a brick-shaped virus with a single linear molecule of double stranded DNA and is a member of the Poxviridae family. Variola virus was the causative agent of smallpox that multiplied in the lymph nodes.

Question 71

Which of the following clinical conditions is associated with the Coxsackievirus type B? ## Footnote 1 Hepatocellular carcinoma 2 Cervical cancer 3 Herpangia 4 Bone break fever 5 Gingivostomatitis 6 Tick-borne encephalitis 7 Smallpox 8 Bornholm disease

Answer 71

Bornholm disease ## Footnote Majority of cervical cancers (approximately 90%) contain human papilloma virus DNA, usually of type 16 or 18. Human papilloma viruses are members of the family Papovaviridae and have predilection for the skin and mucous membranes. Human papilloma viruses are associated with warts, respiratory papillomas, oral infections, and genital infections. Human papilloma viral infection may progress over a period of years through the various stages of cervical intraepithelial neoplasia to invasive squamous carcinoma. Hepatitis B virus (HBV) is a human carcinogen associated with hepatocellular carcinoma. The incidence of hepatocellular carcinoma is higher in a person who becomes infected with HBV earlier in life. The pattern observed is: person develops chronic hepatitis leading to cirrhosis of the liver and eventually to liver cancer 20-50 years post-infection. The genome of HBV is small and comprises a small, circular, partially double stranded DNA molecule. HBV replicates in hepatocyte and involves RNA intermediate and a virus coded reverse transcriptase. HBV can become integrated into the cellular chromosome during chronic infection and may promote genetic instability in the cell. Dengue fever virus and Powassan virus are members of the family Flaviviridae. Flaviviruses are enveloped viruses with icosahedral symmetry. The genome consists of a linear single stranded RNA molecule and replication occurs in the cytoplasm. Dengue fever virus is transmitted by the mosquito and is associated with bone break fever and dengue shock syndrome. Bone break fever is characterized by headache, myalgia, arthralgia, and rash. Secondary exposure can result in dengue shock syndrome and is characterized by gastrointestinal hemorrhage. Powassan virus is associated with tick-borne virus encephalitis. Ixodes tick is the vector for Powassan virus. Domestic animals can play a role in the spread of the disease, as the tick can bite the domestic and farm animals and humans can be infected by the ingestion of raw milk or tick bite. Herpes simplex virus type 1 (HSV-1) is a member of the Herpesviridae family and consists of a double stranded DNA genome. Primary infection with HSV-1 mostly involves the mouth and/or throat. Gingivostomatitis is a classic clinical presentation of HSV-1 infection. It is characterized by formation of vesicles on the mouth and gums, which rupture to become ulcers. Coxsackievirus type A and coxsackievirus type B are members of the Picornaviridae family. Picornaviruses are naked viruses with an icosahedral nucleocapsid. The genome consists of single molecule of single stranded RNA. Coxsackievirus type A is associated with herpangina, which is commonly seen in children. Herpangina is a severe febrile pharyngitis characterized by vesicles or nodules primarily on the soft palate. Coxsackievirus type B is associated with Bornholm disease seen mainly in older children and young adults. Bornholm disease is myositis and is also called Pleurodynia. It is characterized by paroxysms of stabbing pain in the chest muscles and abdomen muscles. Variola virus is a brick-shaped virus with a single linear molecule of double stranded DNA and is a member of the Poxviridae family. Variola virus was the causative agent of smallpox that multiplied in the lymph nodes. Smallpox is an ancient disease that is eradicated.

Question 72

Which of the following clinical conditions is associated with variola? ## Footnote 1 Hepatocellular carcinoma 2 Cervical cancer 3 Herpangia 4 Bone break fever 5 Gingivostomatitis 6 Tick-borne encephalitis 7 Smallpox 8 Bornholm disease

Answer 72

Smallpox ## Footnote Majority of cervical cancers (approximately 90%) contain human papilloma virus DNA, usually of type 16 or 18. Human papilloma viruses are members of the family Papovaviridae and have predilection for the skin and mucous membranes. Human papilloma viruses are associated with warts, respiratory papillomas, oral infections, and genital infections. Human papilloma viral infection may progress over a period of years through the various stages of cervical intraepithelial neoplasia to invasive squamous carcinoma. Hepatitis B virus (HBV) is a human carcinogen associated with hepatocellular carcinoma. The incidence of hepatocellular carcinoma is higher in a person who becomes infected with HBV earlier in life. The pattern observed is: person develops chronic hepatitis leading to cirrhosis of the liver and eventually to liver cancer 20-50 years post-infection. The genome of HBV is small and comprises a small, circular, partially double stranded DNA molecule. HBV replicates in hepatocyte and involves RNA intermediate and a virus coded reverse transcriptase. HBV can become integrated into the cellular chromosome during chronic infection and may promote genetic instability in the cell. Dengue fever virus and Powassan virus are members of the family Flaviviridae. Flaviviruses are enveloped viruses with icosahedral symmetry. The genome consists of a linear single stranded RNA molecule and replication occurs in the cytoplasm. Dengue fever virus is transmitted by the mosquito and is associated with bone break fever and dengue shock syndrome. Bone break fever is characterized by headache, myalgia, arthralgia, and rash. Secondary exposure can result in dengue shock syndrome and is characterized by gastrointestinal hemorrhage. Powassan virus is associated with tick-borne virus encephalitis. Ixodes tick is the vector for Powassan virus. Domestic animals can play a role in the spread of the disease, as the tick can bite the domestic and farm animals and humans can be infected by the ingestion of raw milk or tick bite. Herpes simplex virus type 1 (HSV-1) is a member of the Herpesviridae family and consists of a double stranded DNA genome. Primary infection with HSV-1 mostly involves the mouth and/or throat. Gingivostomatitis is a classic clinical presentation of HSV-1 infection. It is characterized by formation of vesicles on the mouth and gums, which rupture to become ulcers. Coxsackievirus type A and coxsackievirus type B are members of the Picornaviridae family. Picornaviruses are naked viruses with an icosahedral nucleocapsid. The genome consists of single molecule of single stranded RNA. Coxsackievirus type A is associated with herpangina, which is commonly seen in children. Herpangina is a severe febrile pharyngitis characterized by vesicles or nodules primarily on the soft palate. Coxsackievirus type B is associated with Bornholm disease seen mainly in older children and young adults. Bornholm disease is myositis and is also called Pleurodynia. It is characterized by paroxysms of stabbing pain in the chest muscles and abdomen muscles. Variola virus is a brick-shaped virus with a single linear molecule of double stranded DNA and is a member of the Poxviridae family. Variola virus was the causative agent of smallpox that multiplied in the lymph nodes. Smallpox is an ancient disease that is eradicated.

Question 73

Which of the following viral pathogens is associated with myocarditis and pericarditis? ## Footnote 1 Respiratory syncytial virus, influenza virus, and parainfluenza virus 2 Dengue fever virus and Lassa fever virus 3 Human papilloma viruses and herpes simplex virus type 2 4 Coxsackievirus type B and echoviruses 5 Rotavirus and Norwalk virus

Answer 73

Coxsackievirus type B and echoviruses ## Footnote Viral infection of the heart and cardiac muscles can be presented as myocarditis, pericarditis, or cardiomyopathy, which can cause subsequent damage. Coxsackie B virus and echovirus are associated with myocarditis and pericarditis in newborns, children, and adults characterized by recrudescence, leading to permanent heart damage, cardiomegaly, or congestive heart failure. Coxsackie virus type B and echovirus 11 can infect newborns prenatally, natally, or postnatally, resulting in the encephalomyocarditis syndrome. Viral hemorrhagic fevers are characterized by a widespread hemorrhage from the body's epithelial surface, which includes the internal mucosa (such as gastrointestinal tract). The virus infects the endothelial cell lining of the vasculature and may cause cytolysis that results in increased permeability or rupture of the vessel. Thrombocytopenia, leukopenia, petechiae, and ecchymoses are some of the common presentation. Yellow fever and Dengue shock syndrome can result in death within hours due to hypovolemic shock. Respiratory syncytial virus (RSV), Influenza virus, and parainfluenza 3 viruses are common causes of acute bronchitis. RSV and parainfluenza 3 virus infections in infants younger than 6 months can result in life threatening pneumonia or bronchiolitis. Influenza is a major cause of respiratory infection in the general population. Influenza virus targets and destroys mucus-secreting epithelial cells, leading to the loss of primary defense system. New strains emerge every year and can effect a large population, including the children who are universally susceptible to new strains. Viral infections of the gastrointestinal tract with rotavirus and Norwalk virus can lead to gastroenteritis and diarrhea. These viruses infect the small intestine and damage the epithelial lining and absorptive villi, which can lead to malabsorption with water and electrolyte imbalance. Rotaviruses are a major cause of infantile gastroenteritis, which can cause extensive tissue damage leading to serious fluid and electrolyte loss. Norwalk virus is associated with gastroenteritis in younger children and adults. Genital tract infections by Human papilloma viruses is considered a sexually transmitted disease. HPV type 6 and 11 are mostly implicated in genital warts that are found on the squamous epithelium of the external genitalia and perianal areas. Intraepithelial neoplasia and carcinoma often result from genital tract infections caused by HPV type 16 and 18. Herpes simplex virus type 2 is a major cause of genital herpes, which is another sexually transmitted disease. Primary infection is accompanied by inguinal adenitis, fever, malaise, myalgia, and lesions on genital areas.

Question 74

Which of the following viral pathogens is associated with hemorrhagic fever? Answer Choices ## Footnote 1 Respiratory syncytial virus, influenza virus, and parainfluenza virus 2 Dengue fever virus and Lassa fever virus 3 Human papilloma viruses and herpes simplex virus type 2 4 Coxsackievirus type B and echoviruses 5 Rotavirus and Norwalk virus

Answer 74

Dengue fever virus and Lassa fever virus ## Footnote Viral infection of the heart and cardiac muscles can be presented as myocarditis, pericarditis, or cardiomyopathy, which can cause subsequent damage. Coxsackie B virus and echovirus are associated with myocarditis and pericarditis in newborns, children, and adults characterized by recrudescence, leading to permanent heart damage, cardiomegaly, or congestive heart failure. Coxsackie virus type B and echovirus 11 can infect newborns prenatally, natally, or postnatally, resulting in the encephalomyocarditis syndrome. Viral hemorrhagic fevers are characterized by a widespread hemorrhage from the body's epithelial surface, which includes the internal mucosa (such as gastrointestinal tract). The virus infects the endothelial cell lining of the vasculature and may cause cytolysis that results in increased permeability or rupture of the vessel. Thrombocytopenia, leukopenia, petechiae, and ecchymoses are some of the common presentation. Yellow fever and Dengue shock syndrome can result in death within hours due to hypovolemic shock. Respiratory syncytial virus (RSV), Influenza virus, and parainfluenza 3 viruses are common causes of acute bronchitis. RSV and parainfluenza 3 virus infections in infants younger than 6 months can result in life threatening pneumonia or bronchiolitis. Influenza is a major cause of respiratory infection in the general population. Influenza virus targets and destroys mucus-secreting epithelial cells, leading to the loss of primary defense system. New strains emerge every year and can effect a large population, including the children who are universally susceptible to new strains. Viral infections of the gastrointestinal tract with rotavirus and Norwalk virus can lead to gastroenteritis and diarrhea. These viruses infect the small intestine and damage the epithelial lining and absorptive villi, which can lead to malabsorption with water and electrolyte imbalance. Rotaviruses are a major cause of infantile gastroenteritis, which can cause extensive tissue damage leading to serious fluid and electrolyte loss. Norwalk virus is associated with gastroenteritis in younger children and adults. Genital tract infections by Human papilloma viruses is considered a sexually transmitted disease. HPV type 6 and 11 are mostly implicated in genital warts that are found on the squamous epithelium of the external genitalia and perianal areas. Intraepithelial neoplasia and carcinoma often result from genital tract infections caused by HPV type 16 and 18. Herpes simplex virus type 2 is a major cause of genital herpes, which is another sexually transmitted disease. Primary infection is accompanied by inguinal adenitis, fever, malaise, myalgia, and lesions on genital areas.

Question 75

Which of the following viral pathogens is associated with lower respiratory tract infections? ## Footnote 1 Respiratory syncytial virus, influenza virus, and parainfluenza virus 2 Dengue fever virus and Lassa fever virus 3 Human papilloma viruses and herpes simplex virus type 2 4 Coxsackievirus type B and echoviruses 5 Rotavirus and Norwalk virus

Answer 75

Respiratory syncytial virus, influenza virus, and parainfluenza virus ## Footnote Viral infection of the heart and cardiac muscles can be presented as myocarditis, pericarditis, or cardiomyopathy, which can cause subsequent damage. Coxsackie B virus and echovirus are associated with myocarditis and pericarditis in newborns, children, and adults characterized by recrudescence, leading to permanent heart damage, cardiomegaly, or congestive heart failure. Coxsackie virus type B and echovirus 11 can infect newborns prenatally, natally, or postnatally, resulting in the encephalomyocarditis syndrome. Viral hemorrhagic fevers are characterized by a widespread hemorrhage from the body's epithelial surface, which includes the internal mucosa (such as gastrointestinal tract). The virus infects the endothelial cell lining of the vasculature and may cause cytolysis that results in increased permeability or rupture of the vessel. Thrombocytopenia, leukopenia, petechiae, and ecchymoses are some of the common presentation. Yellow fever and Dengue shock syndrome can result in death within hours due to hypovolemic shock. Respiratory syncytial virus (RSV), Influenza virus, and parainfluenza 3 viruses are common causes of acute bronchitis. RSV and parainfluenza 3 virus infections in infants younger than 6 months can result in life threatening pneumonia or bronchiolitis. Influenza is a major cause of respiratory infection in the general population. Influenza virus targets and destroys mucus-secreting epithelial cells, leading to the loss of primary defense system. New strains emerge every year and can effect a large population, including the children who are universally susceptible to new strains. Viral infections of the gastrointestinal tract with rotavirus and Norwalk virus can lead to gastroenteritis and diarrhea. These viruses infect the small intestine and damage the epithelial lining and absorptive villi, which can lead to malabsorption with water and electrolyte imbalance. Rotaviruses are a major cause of infantile gastroenteritis, which can cause extensive tissue damage leading to serious fluid and electrolyte loss. Norwalk virus is associated with gastroenteritis in younger children and adults. Genital tract infections by Human papilloma viruses is considered a sexually transmitted disease. HPV type 6 and 11 are mostly implicated in genital warts that are found on the squamous epithelium of the external genitalia and perianal areas. Intraepithelial neoplasia and carcinoma often result from genital tract infections caused by HPV type 16 and 18. Herpes simplex virus type 2 is a major cause of genital herpes, which is another sexually transmitted disease. Primary infection is accompanied by inguinal adenitis, fever, malaise, myalgia, and lesions on genital areas.

Question 76

Which of the following viral pathogens is associated with gastroenteritis? ## Footnote 1 Respiratory syncytial virus, influenza virus, parainfluenza virus 2 Dengue fever virus and Lassa fever virus 3 Human papilloma viruses and herpes simplex virus type 2 4 Coxsackievirus type B and echoviruses 5 Rotavirus and Norwalk virus

Answer 76

Rotavirus and Norwalk virus ## Footnote Viral infection of the heart and cardiac muscles can be presented as myocarditis, pericarditis, or cardiomyopathy, which can cause subsequent damage. Coxsackie B virus and echovirus are associated with myocarditis and pericarditis in newborns, children, and adults characterized by recrudescence, leading to permanent heart damage, cardiomegaly, or congestive heart failure. Coxsackie virus type B and echovirus 11 can infect newborns prenatally, natally, or postnatally, resulting in the encephalomyocarditis syndrome. Viral hemorrhagic fevers are characterized by a widespread hemorrhage from the body's epithelial surface, which includes the internal mucosa (such as gastrointestinal tract). The virus infects the endothelial cell lining of the vasculature and may cause cytolysis that results in increased permeability or rupture of the vessel. Thrombocytopenia, leukopenia, petechiae, and ecchymoses are some of the common presentation. Yellow fever and Dengue shock syndrome can result in death within hours due to hypovolemic shock. Respiratory syncytial virus (RSV), Influenza virus, and parainfluenza 3 viruses are common causes of acute bronchitis. RSV and parainfluenza 3 virus infections in infants younger than 6 months can result in life threatening pneumonia or bronchiolitis. Influenza is a major cause of respiratory infection in the general population. Influenza virus targets and destroys mucus-secreting epithelial cells, leading to the loss of primary defense system. New strains emerge every year and can effect a large population, including the children who are universally susceptible to new strains. Viral infections of the gastrointestinal tract with rotavirus and Norwalk virus can lead to gastroenteritis and diarrhea. These viruses infect the small intestine and damage the epithelial lining and absorptive villi, which can lead to malabsorption with water and electrolyte imbalance. Rotaviruses are a major cause of infantile gastroenteritis, which can cause extensive tissue damage leading to serious fluid and electrolyte loss. Norwalk virus is associated with gastroenteritis in younger children and adults. Genital tract infections by Human papilloma viruses is considered a sexually transmitted disease. HPV type 6 and 11 are mostly implicated in genital warts that are found on the squamous epithelium of the external genitalia and perianal areas. Intraepithelial neoplasia and carcinoma often result from genital tract infections caused by HPV type 16 and 18. Herpes simplex virus type 2 is a major cause of genital herpes, which is another sexually transmitted disease. Primary infection is accompanied by inguinal adenitis, fever, malaise, myalgia, and lesions on genital areas.

Question 77

Which of the following viral pathogens is associated with genital diseases? ## Footnote 1 Respiratory syncytial virus, influenza virus, parainfluenza virus 2 Dengue fever virus and Lassa fever virus 3 Human papilloma viruses and herpes simplex virus type 2 4 Coxsackievirus type B and echoviruses 5 Rotavirus and Norwalk virus

Answer 77

Human papilloma viruses and herpes simplex virus type 2 ## Footnote Viral infection of the heart and cardiac muscles can be presented as myocarditis, pericarditis, or cardiomyopathy, which can cause subsequent damage. Coxsackie B virus and echovirus are associated with myocarditis and pericarditis in newborns, children, and adults characterized by recrudescence, leading to permanent heart damage, cardiomegaly, or congestive heart failure. Coxsackie virus type B and echovirus 11 can infect newborns prenatally, natally, or postnatally, resulting in the encephalomyocarditis syndrome. Viral hemorrhagic fevers are characterized by a widespread hemorrhage from the body's epithelial surface, which includes the internal mucosa (such as gastrointestinal tract). The virus infects the endothelial cell lining of the vasculature and may cause cytolysis that results in increased permeability or rupture of the vessel. Thrombocytopenia, leukopenia, petechiae, and ecchymoses are some of the common presentation. Yellow fever and Dengue shock syndrome can result in death within hours due to hypovolemic shock. Respiratory syncytial virus (RSV), Influenza virus, and parainfluenza 3 viruses are common causes of acute bronchitis. RSV and parainfluenza 3 virus infections in infants younger than 6 months can result in life threatening pneumonia or bronchiolitis. Influenza is a major cause of respiratory infection in the general population. Influenza virus targets and destroys mucus-secreting epithelial cells, leading to the loss of primary defense system. New strains emerge every year and can effect a large population, including the children who are universally susceptible to new strains. Viral infections of the gastrointestinal tract with rotavirus and Norwalk virus can lead to gastroenteritis and diarrhea. These viruses infect the small intestine and damage the epithelial lining and absorptive villi, which can lead to malabsorption with water and electrolyte imbalance. Rotaviruses are a major cause of infantile gastroenteritis, which can cause extensive tissue damage leading to serious fluid and electrolyte loss. Norwalk virus is associated with gastroenteritis in younger children and adults. Genital tract infections by Human papilloma viruses is considered a sexually transmitted disease. HPV type 6 and 11 are mostly implicated in genital warts that are found on the squamous epithelium of the external genitalia and perianal areas. Intraepithelial neoplasia and carcinoma often result from genital tract infections caused by HPV type 16 and 18. Herpes simplex virus type 2 is a major cause of genital herpes, which is another sexually transmitted disease. Primary infection is accompanied by inguinal adenitis, fever, malaise, myalgia, and lesions on genital areas.

Question 78

Which of the following is true of human adenoviruses? ## Footnote 1 They are enveloped viruses with helical nucleocapsid. 2 Genome consists of a circular single stranded RNA. 3 Encodes for its own DNA polymerase. 4 Forms acidophilic intracytoplasmic inclusions. 5 Replication occurs in the cytoplasm.

Answer 78

Encodes for its own DNA polymerase. ## Footnote Adenoviruses are non-enveloped viruses with an icosahedral nucleocapsid. The capsid contains 12 pentons at each vertices with 12 fibers projecting from the vertices. The genome is a linear double stranded DNA with terminal protein. Viral attachment proteins are present in the fibers projecting from the vertices of the virions. The additional characteristics of adenovirus include the following: The virions replicate in the nucleus. Encode proteins to promote mRNA and DNA synthesis, including its own DNA polymerase. Infects epithelial cells lining respiratory and enteric organs. Virus can become latent in lymphoid tissue and can be reactivated by immunosuppression or infection with other agents. Forms basophilic intranuclear inclusions within an infected epithelial cell. Commonly associated with respiratory diseases, adenoviral pneumonia, epidemic keratoconjunctivitis, and pharyngoconjunctival fever.

Question 79

The etiological agent of acquired immune deficiency syndrome belongs to the family ## Footnote 1 Paramyxoviridae 2 Retroviridae 3 Arenaviridae 4 Togaviridae 5 Reoviridae

Answer 79

Retroviridae ## Footnote Human immunodeficiency virus (HIV) is the etiological agent of acquired immune deficiency syndrome and is a member of the family Retroviridae. Retrovirus encodes reverse transcriptase (an RNA dependent DNA polymerase) and replicate through DNA intermediate. The newly synthesized DNA is integrated into a host chromosome to become a cellular gene. Retroviruses are enveloped RNA viruses with a three layer structure. Genome-nucleoprotein complex is the innermost structure with several molecules of enzymes - reverse transcriptase, integrase, and protease enclosed within a capsid. The HIV virions capsid appears cone-shaped and contains some minor proteins. The capsid of HIV is surrounded by an envelope that contains oligomers of a glycoprotein. Retroviruses are the only virions with diploid genome with the following unique characteristics: Consists of two haploid segment of a single-stranded RNA. Does not encode polymerase to directly generate more mRNA. Viral RNA is synthesized and processed by mRNA-processing machinery of the cell. Involves a specific tRNA whose function is primarily replication.

Question 80

Human immunodeficiency virus shows tropism for ## Footnote 1 Reticulocyte 2 B lymphocyte 3 CD4+ T lymphocytes 4 Hepatocytes 5 Thrombocyte

Answer 80

CD4+ T lymphocytes ## Footnote Human immunodeficiency virus (HIV) shows tropism for CD4+ T lymphocytes and macrophages. CD4+ T lymphocytes are helper and delayed type hypersensitivity T cells. HIV remains latent in the T cells for long periods but destroys the cells when activated. Glycoprotein gp120 is present on the surface of HIV and binds tightly to CD4 and stops its cell surface expression and immunological function, causing syncytia formation that ultimately leads to cell lysis.

Question 81

A 1-year-old boy presents with a "barking" cough and inspiratory stridor. What virus is the probable causative agent of the infant’s illness? ## Footnote 1 Respiratory syncytial virus 2 Influenza A 3 Adenovirus 4 Parainfluenza virus 5 Rhinovirus

Answer 81

Parainfluenza virus ## Footnote The child has the characteristic symptoms of laryngotracheobronchitis, commonly known as croup. All of the listed viruses can cause respiratory tract infections in infants and young children, each producing different clinical manifestations. Parainfluenza virus is the most common agent of croup. Types 1 and 2 are particularly associated with this disease. Croup is characterized by respiratory obstruction due to swelling of the larynx and related structures. Infection may spread deeper to the lower trachea and bronchi, culminating in pneumonia and bronchitis. The infection is seen mostly in 6- to 18-month-old children. Respiratory syncytial virus is mostly associated with bronchiolitis and pneumonia. Influenza virus is also one of the agents of laryngotracheitis in infants, though not as frequently as the parainfluenza viruses. The virus can be responsible for pneumonia in infants. Adenoviruses cause common cold-like symptoms and upper respiratory tract infection. Certain serotypes, particularly types 3, 7, and 21, cause pneumonia in children. Mortality rates are higher in the very young. Rhinoviruses are agents of the common cold.

Question 82

Which of the following is the primary cause of cold sores? ## Footnote 1 Herpes simplex virus 2 Lassa fever virus 3 JC virus 4 Parainfluenza 1 5 Coxsackievirus A16 6 Human T-lymphotropic virus 7 Human rotavirus 8 Pox virus 9 Epstein-Barr virus 10 Human immunodeficiency virus

Answer 82

Herpes simplex virus ## Footnote Laryngotracheobronchitis, commonly known as croup, is one of the serious manifestation of parainfluenza virus infection in infants and young children. Parainfluenza type 1 is a common cause of croup, which results in subglottal swelling and airway obstruction. Major clinical manifestations include hoarseness, "barking" cough, tachypnea, tachycardia, and suprasternal retraction. Cold sore is a recurrent mucocutaneous infection caused by herpes simplex virus (HSV). The individual retains HSV-1 DNA in the trigeminal ganglion for life following recovery from primary oropharyngeal HSV infection. Cold sores, also known as herpetic labialis, are manifested as a result of activation of HSV from the trigeminal ganglia. Cold sores are characterized by development of a cluster of vesicles around the mucocutaneous junction of the lips. Rotaviruses can survive the acidic environment in stomach. The virus infects the small intestine and damages the epithelial cell lining the villi. The virus causes permeability changes and cell lysis, leading to malabsorption with water and electrolyte imbalance. Rotaviruses are a major cause of diarrhea in young children and are associated with outbreaks in preschool and day care-centers. Rotaviruses cause extensive tissue damage, leading to serious fluid and electrolyte loss. Lassa fever virus is an Arenavirus associated with hemorrhagic fever. Lassa fever virus is enzootic in the West African peridomestic rodent. The rodent transmits the virus to the human by contaminating the house with urine. The infection is characterized by fever, headache, malaise, coagulopathy, petechiae, vomiting, pharyngitis, and occasional visceral hemorrhage. Serious manifestations include carditis, hepatitis, encephalopathy, pneumonitis, conjunctivitis, etc. Cardiovascular collapse results in death in 20% of the hospitalized cases. Hand, foot, and mouth disease is a vesicular exanthem caused by coxsackievirus A16. It is characterized by ulcerating vesicles on hand, foot, mouth, and tongue along with mild fever. The disease subsides in a few days on its own. JC virus is a papovavirus associated with progressive multifocal leukoencephalopathy (PML) in immunocompromised patients, including AIDS. PML is a subacute demyelinating disease of the central nervous system, which is primarily seen as a complication of advanced disseminated malignant conditions (such as Hodgkin's disease or chronic lymphocytic leukemia). The patient presents with multiple neurological symptoms, which are not attributable to a single anatomical lesion. Clinical manifestations include impairment of vision, speech, and coordination that can lead to paralysis and death. Tropical spastic paraparesis (TSP) is a progressive demyelination of the long motor neuron tract in the spinal cord. Human T-lymphotropic virus-1 is the causative agent of TSP, which is primarily seen in 20 to 50-year-old women. TSP starts with lumbar back pain radiating down the legs and leads to weakness and spastic paralysis of the lower limbs. Epstein-Barr virus (EBV) infection in adolescence results in infectious mononucleosis and is characterized by an increase in atypical lymphocytes in peripheral blood. The clinical manifestations are fever, malaise, fatigue, pharyngitis, and generalized lymphadenopathy and hepatosplenomegaly. Serious complications include laryngeal obstruction, hemolytic anemia, thrombocytopenia, nephritis, pneumonia, spleen rupture, and neurological disorders. Kaposi's sarcoma is one of the most common malignancies seen in patients infected with Human Immunodeficiency Virus (HIV). The CD4 cell count decreases in HIV infected individuals. Kaposi's sarcoma presents in HIV infected individuals as an invasive and slowly progressive skin cancer that disseminates to visceral organs. Pox virus is the etiological agent of molluscum contagiosum and is spread by direct contact or by fomites. Lesions of molluscum contagiosum are nodular or wartlike and begin as papules. The lesions occur in a cluster of 5 to 20 nodules and are commonly found on trunk, genitalia, and proximal extremities. Histological examination of biopsy material reveals molluscum bodies. Molluscum bodies are the intracytoplasmic inclusion found in epithelial cells of the lesions.

Question 83

Which of the following is a major cause of serious diarrhea in young children? ## Footnote 1 Herpes simplex virus 2 Lassa fever virus 3 JC virus 4 Parainfluenza 1 5 Coxsackievirus A16 6 Human T-lymphotropic virus 7 Human rotavirus 8 Pox virus 9 Epstein-Barr virus 10 Human immunodeficiency virus

Answer 83

Human rotavirus ## Footnote Laryngotracheobronchitis, commonly known as croup, is one of the serious manifestation of parainfluenza virus infection in infants and young children. Parainfluenza type 1 is a common cause of croup, which results in subglottal swelling and airway obstruction. Major clinical manifestations include hoarseness, "barking" cough, tachypnea, tachycardia, and suprasternal retraction. Cold sore is a recurrent mucocutaneous infection caused by herpes simplex virus (HSV). The individual retains HSV-1 DNA in the trigeminal ganglion for life following recovery from primary oropharyngeal HSV infection. Cold sores, also known as herpetic labialis, are manifested as a result of activation of HSV from the trigeminal ganglia. Cold sores are characterized by development of a cluster of vesicles around the mucocutaneous junction of the lips. Rotaviruses can survive the acidic environment in stomach. The virus infects the small intestine and damages the epithelial cell lining the villi. The virus causes permeability changes and cell lysis, leading to malabsorption with water and electrolyte imbalance. Rotaviruses are a major cause of diarrhea in young children and are associated with outbreaks in preschool and day care-centers. Rotaviruses cause extensive tissue damage, leading to serious fluid and electrolyte loss. Lassa fever virus is an Arenavirus associated with hemorrhagic fever. Lassa fever virus is enzootic in the West African peridomestic rodent. The rodent transmits the virus to the human by contaminating the house with urine. The infection is characterized by fever, headache, malaise, coagulopathy, petechiae, vomiting, pharyngitis, and occasional visceral hemorrhage. Serious manifestations include carditis, hepatitis, encephalopathy, pneumonitis, conjunctivitis, etc. Cardiovascular collapse results in death in 20% of the hospitalized cases. Hand, foot, and mouth disease is a vesicular exanthem caused by coxsackievirus A16. It is characterized by ulcerating vesicles on hand, foot, mouth, and tongue along with mild fever. The disease subsides in a few days on its own. JC virus is a papovavirus associated with progressive multifocal leukoencephalopathy (PML) in immunocompromised patients, including AIDS. PML is a subacute demyelinating disease of the central nervous system, which is primarily seen as a complication of advanced disseminated malignant conditions (such as Hodgkin's disease or chronic lymphocytic leukemia). The patient presents with multiple neurological symptoms, which are not attributable to a single anatomical lesion. Clinical manifestations include impairment of vision, speech, and coordination that can lead to paralysis and death. Tropical spastic paraparesis (TSP) is a progressive demyelination of the long motor neuron tract in the spinal cord. Human T-lymphotropic virus-1 is the causative agent of TSP, which is primarily seen in 20 to 50-year-old women. TSP starts with lumbar back pain radiating down the legs and leads to weakness and spastic paralysis of the lower limbs. Epstein-Barr virus (EBV) infection in adolescence results in infectious mononucleosis and is characterized by an increase in atypical lymphocytes in peripheral blood. The clinical manifestations are fever, malaise, fatigue, pharyngitis, and generalized lymphadenopathy and hepatosplenomegaly. Serious complications include laryngeal obstruction, hemolytic anemia, thrombocytopenia, nephritis, pneumonia, spleen rupture, and neurological disorders. Kaposi's sarcoma is one of the most common malignancies seen in patients infected with Human Immunodeficiency Virus (HIV). The CD4 cell count decreases in HIV infected individuals. Kaposi's sarcoma presents in HIV infected individuals as an invasive and slowly progressive skin cancer that disseminates to visceral organs. Pox virus is the etiological agent of molluscum contagiosum and is spread by direct contact or by fomites. Lesions of molluscum contagiosum are nodular or wartlike and begin as papules. The lesions occur in a cluster of 5 to 20 nodules and are commonly found on trunk, genitalia, and proximal extremities. Histological examination of biopsy material reveals molluscum bodies. Molluscum bodies are the intracytoplasmic inclusion found in epithelial cells of the lesions.

Question 84

Which of the following is the etiological agent of hemorrhagic fever that is endemic in West Africa? ## Footnote 1 Herpes simplex virus 2 Lassa fever virus 3 JC virus 4 Parainfluenza 1 5 Coxsackievirus A16 6 Human T-lymphotropic virus 7 Human rotavirus 8 Pox virus 9 Epstein-Barr virus 10 Human immunodeficiency virus

Answer 84

Lassa fever virus ## Footnote Laryngotracheobronchitis, commonly known as croup, is one of the serious manifestation of parainfluenza virus infection in infants and young children. Parainfluenza type 1 is a common cause of croup, which results in subglottal swelling and airway obstruction. Major clinical manifestations include hoarseness, "barking" cough, tachypnea, tachycardia, and suprasternal retraction. Cold sore is a recurrent mucocutaneous infection caused by herpes simplex virus (HSV). The individual retains HSV-1 DNA in the trigeminal ganglion for life following recovery from primary oropharyngeal HSV infection. Cold sores, also known as herpetic labialis, are manifested as a result of activation of HSV from the trigeminal ganglia. Cold sores are characterized by development of a cluster of vesicles around the mucocutaneous junction of the lips. Rotaviruses can survive the acidic environment in stomach. The virus infects the small intestine and damages the epithelial cell lining the villi. The virus causes permeability changes and cell lysis, leading to malabsorption with water and electrolyte imbalance. Rotaviruses are a major cause of diarrhea in young children and are associated with outbreaks in preschool and day care-centers. Rotaviruses cause extensive tissue damage, leading to serious fluid and electrolyte loss. Lassa fever virus is an Arenavirus associated with hemorrhagic fever. Lassa fever virus is enzootic in the West African peridomestic rodent. The rodent transmits the virus to the human by contaminating the house with urine. The infection is characterized by fever, headache, malaise, coagulopathy, petechiae, vomiting, pharyngitis, and occasional visceral hemorrhage. Serious manifestations include carditis, hepatitis, encephalopathy, pneumonitis, conjunctivitis, etc. Cardiovascular collapse results in death in 20% of the hospitalized cases. Hand, foot, and mouth disease is a vesicular exanthem caused by coxsackievirus A16. It is characterized by ulcerating vesicles on hand, foot, mouth, and tongue along with mild fever. The disease subsides in a few days on its own. JC virus is a papovavirus associated with progressive multifocal leukoencephalopathy (PML) in immunocompromised patients, including AIDS. PML is a subacute demyelinating disease of the central nervous system, which is primarily seen as a complication of advanced disseminated malignant conditions (such as Hodgkin's disease or chronic lymphocytic leukemia). The patient presents with multiple neurological symptoms, which are not attributable to a single anatomical lesion. Clinical manifestations include impairment of vision, speech, and coordination that can lead to paralysis and death. Tropical spastic paraparesis (TSP) is a progressive demyelination of the long motor neuron tract in the spinal cord. Human T-lymphotropic virus-1 is the causative agent of TSP, which is primarily seen in 20 to 50-year-old women. TSP starts with lumbar back pain radiating down the legs and leads to weakness and spastic paralysis of the lower limbs. Epstein-Barr virus (EBV) infection in adolescence results in infectious mononucleosis and is characterized by an increase in atypical lymphocytes in peripheral blood. The clinical manifestations are fever, malaise, fatigue, pharyngitis, and generalized lymphadenopathy and hepatosplenomegaly. Serious complications include laryngeal obstruction, hemolytic anemia, thrombocytopenia, nephritis, pneumonia, spleen rupture, and neurological disorders. Kaposi's sarcoma is one of the most common malignancies seen in patients infected with Human Immunodeficiency Virus (HIV). The CD4 cell count decreases in HIV infected individuals. Kaposi's sarcoma presents in HIV infected individuals as an invasive and slowly progressive skin cancer that disseminates to visceral organs. Pox virus is the etiological agent of molluscum contagiosum and is spread by direct contact or by fomites. Lesions of molluscum contagiosum are nodular or wartlike and begin as papules. The lesions occur in a cluster of 5 to 20 nodules and are commonly found on trunk, genitalia, and proximal extremities. Histological examination of biopsy material reveals molluscum bodies. Molluscum bodies are the intracytoplasmic inclusion found in epithelial cells of the lesions.

Question 85

Which of the following is the most common cause of hand, foot, and mouth disease? ## Footnote 1 Herpes simplex virus 2 Lassa fever virus 3 JC virus 4 Parainfluenza 1 5 Coxsackievirus A16 6 Human T-lymphotropic virus 7 Human rotavirus 8 Pox virus 9 Epstein-Barr virus 10 Human immunodeficiency virus

Answer 85

Coxsackievirus A16 ## Footnote Laryngotracheobronchitis, commonly known as croup, is one of the serious manifestation of parainfluenza virus infection in infants and young children. Parainfluenza type 1 is a common cause of croup, which results in subglottal swelling and airway obstruction. Major clinical manifestations include hoarseness, "barking" cough, tachypnea, tachycardia, and suprasternal retraction. Cold sore is a recurrent mucocutaneous infection caused by herpes simplex virus (HSV). The individual retains HSV-1 DNA in the trigeminal ganglion for life following recovery from primary oropharyngeal HSV infection. Cold sores, also known as herpetic labialis, are manifested as a result of activation of HSV from the trigeminal ganglia. Cold sores are characterized by development of a cluster of vesicles around the mucocutaneous junction of the lips. Rotaviruses can survive the acidic environment in stomach. The virus infects the small intestine and damages the epithelial cell lining the villi. The virus causes permeability changes and cell lysis, leading to malabsorption with water and electrolyte imbalance. Rotaviruses are a major cause of diarrhea in young children and are associated with outbreaks in preschool and day care-centers. Rotaviruses cause extensive tissue damage, leading to serious fluid and electrolyte loss. Lassa fever virus is an Arenavirus associated with hemorrhagic fever. Lassa fever virus is enzootic in the West African peridomestic rodent. The rodent transmits the virus to the human by contaminating the house with urine. The infection is characterized by fever, headache, malaise, coagulopathy, petechiae, vomiting, pharyngitis, and occasional visceral hemorrhage. Serious manifestations include carditis, hepatitis, encephalopathy, pneumonitis, conjunctivitis, etc. Cardiovascular collapse results in death in 20% of the hospitalized cases. Hand, foot, and mouth disease is a vesicular exanthem caused by coxsackievirus A16. It is characterized by ulcerating vesicles on hand, foot, mouth, and tongue along with mild fever. The disease subsides in a few days on its own. JC virus is a papovavirus associated with progressive multifocal leukoencephalopathy (PML) in immunocompromised patients, including AIDS. PML is a subacute demyelinating disease of the central nervous system, which is primarily seen as a complication of advanced disseminated malignant conditions (such as Hodgkin's disease or chronic lymphocytic leukemia). The patient presents with multiple neurological symptoms, which are not attributable to a single anatomical lesion. Clinical manifestations include impairment of vision, speech, and coordination that can lead to paralysis and death. Tropical spastic paraparesis (TSP) is a progressive demyelination of the long motor neuron tract in the spinal cord. Human T-lymphotropic virus-1 is the causative agent of TSP, which is primarily seen in 20 to 50-year-old women. TSP starts with lumbar back pain radiating down the legs and leads to weakness and spastic paralysis of the lower limbs. Epstein-Barr virus (EBV) infection in adolescence results in infectious mononucleosis and is characterized by an increase in atypical lymphocytes in peripheral blood. The clinical manifestations are fever, malaise, fatigue, pharyngitis, and generalized lymphadenopathy and hepatosplenomegaly. Serious complications include laryngeal obstruction, hemolytic anemia, thrombocytopenia, nephritis, pneumonia, spleen rupture, and neurological disorders. Kaposi's sarcoma is one of the most common malignancies seen in patients infected with Human Immunodeficiency Virus (HIV). The CD4 cell count decreases in HIV infected individuals. Kaposi's sarcoma presents in HIV infected individuals as an invasive and slowly progressive skin cancer that disseminates to visceral organs. Pox virus is the etiological agent of molluscum contagiosum and is spread by direct contact or by fomites. Lesions of molluscum contagiosum are nodular or wartlike and begin as papules. The lesions occur in a cluster of 5 to 20 nodules and are commonly found on trunk, genitalia, and proximal extremities. Histological examination of biopsy material reveals molluscum bodies. Molluscum bodies are the intracytoplasmic inclusion found in epithelial cells of the lesions.

Question 86

What is the viral agent associated with progressive multifocal leukoencephalopathy in immunocompromised patients? ## Footnote 1Herpes simplex virus 2 Lassa fever virus 3 JC virus 4 Parainfluenza 1 5 Coxsackievirus A16

Answer 86

JC virus ## Footnote is a papovavirus associated with progressive multifocal leukoencephalopathy (PML) in immunocompromised patients, including AIDS. PML is a subacute demyelinating disease of the central nervous system, which is primarily seen as a complication of advanced disseminated malignant conditions (such as Hodgkin's disease or chronic lymphocytic leukemia). The patient presents with multiple neurological symptoms; the symptoms are not attributable to a single anatomical lesion. Clinical manifestations include impairment of vision, speech, and coordination that can lead to paralysis and death. Laryngotracheobronchitis, commonly known as croup, is one of the serious manifestations of parainfluenza virus infection in infants and young children. Parainfluenza type 1 is a common cause of croup that results in subglottal swelling and airway obstruction. Major clinical manifestations include hoarseness, "barking" cough, tachypnea, tachycardia, and suprasternal retraction. Cold sore is a recurrent mucocutaneous infection caused by herpes simplex virus (HSV). The individual retains HSV-1 DNA in the trigeminal ganglion for life following recovery from primary oropharyngeal HSV infection. Cold sores, also known as herpetic labialis, are manifested as a result of activation of HSV from the trigeminal ganglia. Cold sores are characterized by development of a cluster of vesicles around the mucocutaneous junction of the lips. Lassa fever virus is an Arenavirus associated with hemorrhagic fever. Lassa fever virus is enzootic in the West African peridomestic rodent. The rodent transmits the virus to the human by contaminating the house with urine. The infection is characterized by fever, headache, malaise, coagulopathy, petechiae, vomiting, pharyngitis, and occasional visceral hemorrhage. Serious manifestations include carditis, hepatitis, encephalopathy, pneumonitis, conjunctivitis, etc. Cardiovascular collapse results in death in 20% of the hospitalized cases. Hand, foot, and mouth disease is a vesicular exanthem caused by coxsackievirus A16. It is characterized by ulcerating vesicles on hand, foot, mouth, and tongue along with mild fever.

Question 87

Which of the following is the etiological agent of tropical spastic paraparesis? ## Footnote 1 Herpes simplex virus 2 Lassa fever virus 3 JC virus 4 Parainfluenza 1 5 Coxsackievirus A16 6 Human T-lymphotropic virus 7 Human rotavirus 8 Pox virus 9 Epstein-Barr virus 10 Human immunodeficiency virus

Answer 87

Human T-lymphotropic virus ## Footnote Laryngotracheobronchitis, commonly known as croup, is one of the serious manifestation of parainfluenza virus infection in infants and young children. Parainfluenza type 1 is a common cause of croup, which results in subglottal swelling and airway obstruction. Major clinical manifestations include hoarseness, "barking" cough, tachypnea, tachycardia, and suprasternal retraction. Cold sore is a recurrent mucocutaneous infection caused by herpes simplex virus (HSV). The individual retains HSV-1 DNA in the trigeminal ganglion for life following recovery from primary oropharyngeal HSV infection. Cold sores, also known as herpetic labialis, are manifested as a result of activation of HSV from the trigeminal ganglia. Cold sores are characterized by development of a cluster of vesicles around the mucocutaneous junction of the lips. Rotaviruses can survive the acidic environment in stomach. The virus infects the small intestine and damages the epithelial cell lining the villi. The virus causes permeability changes and cell lysis, leading to malabsorption with water and electrolyte imbalance. Rotaviruses are a major cause of diarrhea in young children and are associated with outbreaks in preschool and day care-centers. Rotaviruses cause extensive tissue damage, leading to serious fluid and electrolyte loss. Lassa fever virus is an Arenavirus associated with hemorrhagic fever. Lassa fever virus is enzootic in the West African peridomestic rodent. The rodent transmits the virus to the human by contaminating the house with urine. The infection is characterized by fever, headache, malaise, coagulopathy, petechiae, vomiting, pharyngitis, and occasional visceral hemorrhage. Serious manifestations include carditis, hepatitis, encephalopathy, pneumonitis, conjunctivitis, etc. Cardiovascular collapse results in death in 20% of the hospitalized cases. Hand, foot, and mouth disease is a vesicular exanthem caused by coxsackievirus A16. It is characterized by ulcerating vesicles on hand, foot, mouth, and tongue along with mild fever. The disease subsides in a few days on its own. JC virus is a papovavirus associated with progressive multifocal leukoencephalopathy (PML) in immunocompromised patients, including AIDS. PML is a subacute demyelinating disease of the central nervous system, which is primarily seen as a complication of advanced disseminated malignant conditions (such as Hodgkin's disease or chronic lymphocytic leukemia). The patient presents with multiple neurological symptoms, which are not attributable to a single anatomical lesion. Clinical manifestations include impairment of vision, speech, and coordination that can lead to paralysis and death. Tropical spastic paraparesis (TSP) is a progressive demyelination of the long motor neuron tract in the spinal cord. Human T-lymphotropic virus-1 is the causative agent of TSP, which is primarily seen in 20 to 50-year-old women. TSP starts with lumbar back pain radiating down the legs and leads to weakness and spastic paralysis of the lower limbs. Epstein-Barr virus (EBV) infection in adolescence results in infectious mononucleosis and is characterized by an increase in atypical lymphocytes in peripheral blood. The clinical manifestations are fever, malaise, fatigue, pharyngitis, and generalized lymphadenopathy and hepatosplenomegaly. Serious complications include laryngeal obstruction, hemolytic anemia, thrombocytopenia, nephritis, pneumonia, spleen rupture, and neurological disorders. Kaposi's sarcoma is one of the most common malignancies seen in patients infected with Human Immunodeficiency Virus (HIV). The CD4 cell count decreases in HIV infected individuals. Kaposi's sarcoma presents in HIV infected individuals as an invasive and slowly progressive skin cancer that disseminates to visceral organs. Pox virus is the etiological agent of molluscum contagiosum and is spread by direct contact or by fomites. Lesions of molluscum contagiosum are nodular or wartlike and begin as papules. The lesions occur in a cluster of 5 to 20 nodules and are commonly found on trunk, genitalia, and proximal extremities. Histological examination of biopsy material reveals molluscum bodies. Molluscum bodies are the intracytoplasmic inclusion found in epithelial cells of the lesions.

Question 88

Which of the following is the etiological agent of infectious mononucleosis? ## Footnote 1 Herpes simplex virus 2 Lassa fever virus 3 JC virus 4 Parainfluenza 1 5 Coxsackievirus A16 6 Human T-lymphotropic virus 7 Human rotavirus 8 Pox virus 9 Epstein-Barr virus 10 Human immunodeficiency virus

Answer 88

Epstein-Barr virus ## Footnote Laryngotracheobronchitis, commonly known as croup, is one of the serious manifestation of parainfluenza virus infection in infants and young children. Parainfluenza type 1 is a common cause of croup, which results in subglottal swelling and airway obstruction. Major clinical manifestations include hoarseness, "barking" cough, tachypnea, tachycardia, and suprasternal retraction. Cold sore is a recurrent mucocutaneous infection caused by herpes simplex virus (HSV). The individual retains HSV-1 DNA in the trigeminal ganglion for life following recovery from primary oropharyngeal HSV infection. Cold sores, also known as herpetic labialis, are manifested as a result of activation of HSV from the trigeminal ganglia. Cold sores are characterized by development of a cluster of vesicles around the mucocutaneous junction of the lips. Rotaviruses can survive the acidic environment in stomach. The virus infects the small intestine and damages the epithelial cell lining the villi. The virus causes permeability changes and cell lysis, leading to malabsorption with water and electrolyte imbalance. Rotaviruses are a major cause of diarrhea in young children and are associated with outbreaks in preschool and day care-centers. Rotaviruses cause extensive tissue damage, leading to serious fluid and electrolyte loss. Lassa fever virus is an Arenavirus associated with hemorrhagic fever. Lassa fever virus is enzootic in the West African peridomestic rodent. The rodent transmits the virus to the human by contaminating the house with urine. The infection is characterized by fever, headache, malaise, coagulopathy, petechiae, vomiting, pharyngitis, and occasional visceral hemorrhage. Serious manifestations include carditis, hepatitis, encephalopathy, pneumonitis, conjunctivitis, etc. Cardiovascular collapse results in death in 20% of the hospitalized cases. Hand, foot, and mouth disease is a vesicular exanthem caused by coxsackievirus A16. It is characterized by ulcerating vesicles on hand, foot, mouth, and tongue along with mild fever. The disease subsides in a few days on its own. JC virus is a papovavirus associated with progressive multifocal leukoencephalopathy (PML) in immunocompromised patients, including AIDS. PML is a subacute demyelinating disease of the central nervous system, which is primarily seen as a complication of advanced disseminated malignant conditions (such as Hodgkin's disease or chronic lymphocytic leukemia). The patient presents with multiple neurological symptoms, which are not attributable to a single anatomical lesion. Clinical manifestations include impairment of vision, speech, and coordination that can lead to paralysis and death. Tropical spastic paraparesis (TSP) is a progressive demyelination of the long motor neuron tract in the spinal cord. Human T-lymphotropic virus-1 is the causative agent of TSP, which is primarily seen in 20 to 50-year-old women. TSP starts with lumbar back pain radiating down the legs and leads to weakness and spastic paralysis of the lower limbs. Epstein-Barr virus (EBV) infection in adolescence results in infectious mononucleosis and is characterized by an increase in atypical lymphocytes in peripheral blood. The clinical manifestations are fever, malaise, fatigue, pharyngitis, and generalized lymphadenopathy and hepatosplenomegaly. Serious complications include laryngeal obstruction, hemolytic anemia, thrombocytopenia, nephritis, pneumonia, spleen rupture, and neurological disorders. Kaposi's sarcoma is one of the most common malignancies seen in patients infected with Human Immunodeficiency Virus (HIV). The CD4 cell count decreases in HIV infected individuals. Kaposi's sarcoma presents in HIV infected individuals as an invasive and slowly progressive skin cancer that disseminates to visceral organs. Pox virus is the etiological agent of molluscum contagiosum and is spread by direct contact or by fomites. Lesions of molluscum contagiosum are nodular or wartlike and begin as papules. The lesions occur in a cluster of 5 to 20 nodules and are commonly found on trunk, genitalia, and proximal extremities. Histological examination of biopsy material reveals molluscum bodies. Molluscum bodies are the intracytoplasmic inclusion found in epithelial cells of the lesions.

Question 89

Which of the following is a virus associated with the development of Kaposi's sarcoma? ## Footnote 1 Herpes simplex virus 2 Lassa fever virus 3 JC virus 4 Parainfluenza 1 5 Coxsackievirus A16 6 Human T-lymphotropic virus 7 Human rotavirus 8 Pox virus 9 Epstein-Barr virus 10 Human immunodeficiency virus

Answer 89

Human immunodeficiency virus ## Footnote Laryngotracheobronchitis, commonly known as croup, is one of the serious manifestation of parainfluenza virus infection in infants and young children. Parainfluenza type 1 is a common cause of croup, which results in subglottal swelling and airway obstruction. Major clinical manifestations include hoarseness, "barking" cough, tachypnea, tachycardia, and suprasternal retraction. Cold sore is a recurrent mucocutaneous infection caused by herpes simplex virus (HSV). The individual retains HSV-1 DNA in the trigeminal ganglion for life following recovery from primary oropharyngeal HSV infection. Cold sores, also known as herpetic labialis, are manifested as a result of activation of HSV from the trigeminal ganglia. Cold sores are characterized by development of a cluster of vesicles around the mucocutaneous junction of the lips. Rotaviruses can survive the acidic environment in stomach. The virus infects the small intestine and damages the epithelial cell lining the villi. The virus causes permeability changes and cell lysis, leading to malabsorption with water and electrolyte imbalance. Rotaviruses are a major cause of diarrhea in young children and are associated with outbreaks in preschool and day care-centers. Rotaviruses cause extensive tissue damage, leading to serious fluid and electrolyte loss. Lassa fever virus is an Arenavirus associated with hemorrhagic fever. Lassa fever virus is enzootic in the West African peridomestic rodent. The rodent transmits the virus to the human by contaminating the house with urine. The infection is characterized by fever, headache, malaise, coagulopathy, petechiae, vomiting, pharyngitis, and occasional visceral hemorrhage. Serious manifestations include carditis, hepatitis, encephalopathy, pneumonitis, conjunctivitis, etc. Cardiovascular collapse results in death in 20% of the hospitalized cases. Hand, foot, and mouth disease is a vesicular exanthem caused by coxsackievirus A16. It is characterized by ulcerating vesicles on hand, foot, mouth, and tongue along with mild fever. The disease subsides in a few days on its own. JC virus is a papovavirus associated with progressive multifocal leukoencephalopathy (PML) in immunocompromised patients, including AIDS. PML is a subacute demyelinating disease of the central nervous system, which is primarily seen as a complication of advanced disseminated malignant conditions (such as Hodgkin's disease or chronic lymphocytic leukemia). The patient presents with multiple neurological symptoms, which are not attributable to a single anatomical lesion. Clinical manifestations include impairment of vision, speech, and coordination that can lead to paralysis and death. Tropical spastic paraparesis (TSP) is a progressive demyelination of the long motor neuron tract in the spinal cord. Human T-lymphotropic virus-1 is the causative agent of TSP, which is primarily seen in 20 to 50-year-old women. TSP starts with lumbar back pain radiating down the legs and leads to weakness and spastic paralysis of the lower limbs. Epstein-Barr virus (EBV) infection in adolescence results in infectious mononucleosis and is characterized by an increase in atypical lymphocytes in peripheral blood. The clinical manifestations are fever, malaise, fatigue, pharyngitis, and generalized lymphadenopathy and hepatosplenomegaly. Serious complications include laryngeal obstruction, hemolytic anemia, thrombocytopenia, nephritis, pneumonia, spleen rupture, and neurological disorders. Kaposi's sarcoma is one of the most common malignancies seen in patients infected with Human Immunodeficiency Virus (HIV). The CD4 cell count decreases in HIV infected individuals. Kaposi's sarcoma presents in HIV infected individuals as an invasive and slowly progressive skin cancer that disseminates to visceral organs. Pox virus is the etiological agent of molluscum contagiosum and is spread by direct contact or by fomites. Lesions of molluscum contagiosum are nodular or wartlike and begin as papules. The lesions occur in a cluster of 5 to 20 nodules and are commonly found on trunk, genitalia, and proximal extremities. Histological examination of biopsy material reveals molluscum bodies. Molluscum bodies are the intracytoplasmic inclusion found in epithelial cells of the lesions.

Question 90

Which of the following is the etiological agent of molluscum contagiosum? ## Footnote 1 Herpes simplex virus 2 Lassa fever virus 3 JC virus 4 Parainfluenza 1 5 Coxsackievirus A16 6 Human T-lymphotropic virus 7 Human rotavirus 8 Pox virus 9 Epstein-Barr virus 10 Human immunodeficiency virus

Answer 90

Pox virus ## Footnote Laryngotracheobronchitis, commonly known as croup, is one of the serious manifestation of parainfluenza virus infection in infants and young children. Parainfluenza type 1 is a common cause of croup, which results in subglottal swelling and airway obstruction. Major clinical manifestations include hoarseness, "barking" cough, tachypnea, tachycardia, and suprasternal retraction. Cold sore is a recurrent mucocutaneous infection caused by herpes simplex virus (HSV). The individual retains HSV-1 DNA in the trigeminal ganglion for life following recovery from primary oropharyngeal HSV infection. Cold sores, also known as herpetic labialis, are manifested as a result of activation of HSV from the trigeminal ganglia. Cold sores are characterized by development of a cluster of vesicles around the mucocutaneous junction of the lips. Rotaviruses can survive the acidic environment in stomach. The virus infects the small intestine and damages the epithelial cell lining the villi. The virus causes permeability changes and cell lysis, leading to malabsorption with water and electrolyte imbalance. Rotaviruses are a major cause of diarrhea in young children and are associated with outbreaks in preschool and day care-centers. Rotaviruses cause extensive tissue damage, leading to serious fluid and electrolyte loss. Lassa fever virus is an Arenavirus associated with hemorrhagic fever. Lassa fever virus is enzootic in the West African peridomestic rodent. The rodent transmits the virus to the human by contaminating the house with urine. The infection is characterized by fever, headache, malaise, coagulopathy, petechiae, vomiting, pharyngitis, and occasional visceral hemorrhage. Serious manifestations include carditis, hepatitis, encephalopathy, pneumonitis, conjunctivitis, etc. Cardiovascular collapse results in death in 20% of the hospitalized cases. Hand, foot, and mouth disease is a vesicular exanthem caused by coxsackievirus A16. It is characterized by ulcerating vesicles on hand, foot, mouth, and tongue along with mild fever. The disease subsides in a few days on its own. JC virus is a papovavirus associated with progressive multifocal leukoencephalopathy (PML) in immunocompromised patients, including AIDS. PML is a subacute demyelinating disease of the central nervous system, which is primarily seen as a complication of advanced disseminated malignant conditions (such as Hodgkin's disease or chronic lymphocytic leukemia). The patient presents with multiple neurological symptoms, which are not attributable to a single anatomical lesion. Clinical manifestations include impairment of vision, speech, and coordination that can lead to paralysis and death. Tropical spastic paraparesis (TSP) is a progressive demyelination of the long motor neuron tract in the spinal cord. Human T-lymphotropic virus-1 is the causative agent of TSP, which is primarily seen in 20 to 50-year-old women. TSP starts with lumbar back pain radiating down the legs and leads to weakness and spastic paralysis of the lower limbs. Epstein-Barr virus (EBV) infection in adolescence results in infectious mononucleosis and is characterized by an increase in atypical lymphocytes in peripheral blood. The clinical manifestations are fever, malaise, fatigue, pharyngitis, and generalized lymphadenopathy and hepatosplenomegaly. Serious complications include laryngeal obstruction, hemolytic anemia, thrombocytopenia, nephritis, pneumonia, spleen rupture, and neurological disorders. Kaposi's sarcoma is one of the most common malignancies seen in patients infected with Human Immunodeficiency Virus (HIV). The CD4 cell count decreases in HIV infected individuals. Kaposi's sarcoma presents in HIV infected individuals as an invasive and slowly progressive skin cancer that disseminates to visceral organs. Pox virus is the etiological agent of molluscum contagiosum and is spread by direct contact or by fomites. Lesions of molluscum contagiosum are nodular or wartlike and begin as papules. The lesions occur in a cluster of 5 to 20 nodules and are commonly found on trunk, genitalia, and proximal extremities. Histological examination of biopsy material reveals molluscum bodies. Molluscum bodies are the intracytoplasmic inclusion found in epithelial cells of the lesions.

Question 91

Subacute sclerosing panencephalitis is a late neurological sequelae of infection from what virus? ## Footnote 1 Orthoreovirus 2 Measles virus 3 Hepatitis B virus 4 Papillomavirus 5 Parvovirus B19

Answer 91

Measles virus ## Footnote Subacute sclerosing panencephalitis (SSPE) is a serious, late, and rare neurological complication occurring 1-10 years after recovery from measles. This fatal disease is characterized by a very slow replication and spread of measles virus in the brain. Patients with SSPE do not show a high number of measles viruses in the brain, but they demonstrate unusually high levels of measles antibody in the blood and cerebrospinal fluid. Many years after recovering from measles, patients develop changes in personality, behavior, and memory; those symptoms are followed by myoclonic jerks, blindness, and spasticity. Orthoreovirus mostly causes asymptomatic or mild infections in human. Persistent infection with Hepatitis B can develop into chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Papillomavirus is associated with skin warts, Condyloma acuminatum, genital malignancies, respiratory papillomatosis, and focal epithelial hyperplasia. Parvovirus B19 is the etiological agent of erythema infectiosum primarily seen in children. Parvovirus B19 is also associated with chronic anemia in immunodeficient patients. Infection with this virus during pregnancy can cause anemia and congestive cardiac failure in the fetus and can lead to miscarriage or stillbirth.

Question 92

Case A 21-year-old woman developed a low-grade fever, sore throat, malaise, and fatigue that lasted several days. Physical examination revealed swollen lymph nodes and discomfort in the left upper quadrant of the abdomen. Examination of peripheral blood smear revealed 50% of atypical lymphocytes of the total white cells. Result for heterophile antibody test was positive. What is the most probable cause of infection? ## Footnote 1 Cytomegalovirus 2 Respiratory syncytial virus 3 Influenza virus 4 Epstein-Barr virus 5 Varicella zoster virus

Answer 92

Epstein-Barr virus ## Footnote Epstein-Barr virus and cytomegalovirus elicit a large T-cell response, resulting in a mononucleosis-like syndrome. EBV infection is subclinical and milder in children than adolescents or adults. EBV initiates infection in the epithelial cells of the oropharynx and then spreads to the B lymphocytes in lymphatic tissue and blood. Classical lymphocytosis is associated with the activation and proliferation of suppressor T cells, and it leads to infectious mononucleosis. The atypical lymphocyte, also known as "Downey cells", increases in peripheral blood during the second week of infection. Major T-cell response causes swollen lymph glands, spleen, and liver. Fever, malaise, fatigue, pharyngitis, lymphadenopathy, and hepatosplenomegaly are the classical symptoms associated with infectious mononucleosis. Cytomegalovirus is associated with heterophile-negative mononucleosis. Polyclonal B cell activation by EBV leads to the production of heterophile antibodies, which can be detected by the end of the first week of infection and last for several months. Respiratory syncytial virus, varicella-zoster virus, and influenza virus are not associated with infectious mononucleosis.

Question 93

Prions are associated with slow neurodegenerative disease in humans and animals. Select the most correct statement about prions. ## Footnote 1 Prions are filterable infectious agents 2 Can elicit immune response 3 Consists of RNA 4 Consists of protease sensitive protein 5 Can be inactivated by radiation

Answer 93

Prions are filterable infectious agents ## Footnote Prions are filterable agents that can transmit disease. These unconventional slow agents are associated with subacute spongiform encephalopathy(SSE). SSE are slow neurodegenerative diseases that produce progressive degeneration of neurons and axons of gray matter with characteristic histopathological changes. Prions does not contain RNA or DNA, but consists of protease resistant, hydrophobic glycoprotein. Prions can not be inactivated by radiation. Prions do not generate inflammatory or immune response. SSE caused by prions in human include: Creutzfeldt-Jakob disease (CJD), German-Straussler-Scheinker (GSS) disease, and kuru. Some of the findings of SSE include: Vacuolation of the neurons. Amyloid deposits and fibrils accumulation. Astrocytic proliferation and hypertrophy. Accumulation of the prions in the neurons in high concentrations. CJD is a rare, progressive, fatal disease of the central nervous system which is a genetic human disorder. CJD is transmitted by injection, transplantation of contaminated tissue, or contact with medical devices. GSS is a rare autosomal dominant inherited disease in which there is a single amino acid substitution in the normal cellular prion protein. Kuru, a neurological syndrome characterized by tremors, was limited to a small area in the New Guinea highlands. Kuru has an exceptionally long incubation period and was a major cause of death in women for a certain period of time in this region. Transmission of kuru was related to cannibalistic ceremonies in the Fore tribe of New Guinea.

Question 94

Which of the following best describes human papillomaviruses? ## Footnote 1 Human papillomaviruses are large RNA viruses 2 Human papillomaviruses are small RNA viruses 3 Human papillomaviruses are small DNA viruses 4 Human papillomaviruses are large DNA viruses

Answer 94

Human papillomaviruses are small DNA viruses ## Footnote Human papillomaviruses are small DNA viruses. These viruses replicate in the nuclei of differentiated keratinocytes and are the cause of tumors of the skin and mucosa. The genome of human papillomaviruses is circular and contains approximately 8,000 base pairs.

Question 95

Which statement is true concerning these three sexually transmitted viruses: human papillomavirus, herpes simplex virus, and hepatitis B virus? ## Footnote 1 These viruses all have a genome containing double-stranded DNA. 2 Of these viruses, only human papillomavirus has a genome containing RNA. 3 Of these viruses, only herpes simplex virus has a genome containing RNA. 4 Of these viruses, only hepatitis B virus has a genome containing RNA. 5 These viruses all have a genome containing RNA.

Answer 95

These viruses all have a genome containing double-stranded DNA. ## Footnote Human papillomavirus, herpes simplex virus, and hepatitis B virus are sexually transmitted viruses with double-stranded DNA genomes. While herpes simplex virus has a relatively large genome, the genome of both human papillomavirus and hepatitis B virus are both quite small.

Question 96

Which of the following is true about viruses? ## Footnote 1 Viruses only contain RNA. 2 Viruses infecting bacteria are known as bacteriophages. 3 Viruses are a form of extracellular parasite. 4 Viral integration into the bacterial genome is referred to as phylogeny. 5 The smallest viruses are on the order of 500 nm in diameter.

Answer 96

Viruses infecting bacteria are known as bacteriophages. ## Footnote Viruses infecting bacteria are known as bacteriophages (or simply phages). Viruses may be considered to be a form of intracellular parasite (not extracellular). Viral integration into the bacterial genome is referred to as lysogeny. The smallest viruses are actually on the order of 20 nm in diameter.

Question 97

An in vitro experiment is designed to examine the sequential steps involved in viral infection and replication. Given healthy viable cells and virus, which of the following accurately describes the correct sequence of steps in viral infection and replication? ## Footnote 1 uncoating, attachment, biosynthesis, penetration 2 attachment, uncoating, penetration, biosynthesis 3 attachment, penetration, uncoating, biosynthesis 4 uncoating, attachment, penetration, biosynthesis 5 uncoating, penetration, attachment, biosynthesis

Answer 97

attachment, penetration, uncoating, biosynthesis ## Footnote The first step requires a compatible union between sites on the virus and target cell and likely involves electrostatic interactions. The surface site on the virus may be a spike or fiber of a specific protein. The receptor site on the target cell most typically is a glycoprotein and may be shared by related members of the same virus group. Penetration of the cell can occur via 4 mechanisms. Some viruses may be phagocytized. Alternatively, the viral lipoprotein of the envelope may fuse with the cell membrane. Thirdly, the virus may interact with cell membrane receptor sites, a process in which host cell enzymes start uncoating at the cell membrane, resulting in the nucleic acid (and occasionally its associated polymerase) escaping into the cell. Finally, direct penetration of the intact virus through the cell membrane into the cytoplasm occurs in some viruses. Prior to replication, the viral genome must be extricated from all of the surrounding material. The destruction or disassembly of the capsid may commence while the virion is adsorbing to and penetrating the cell. For some enveloped viruses, elimination of this coating occurs at the surface of the cells. The location of viral synthesis is variable with the nature of the genome (DNA or RNA) and the family or group to which the virus belongs. The DNA of the deoxyribovirus is synthesized in the nucleus of the infected cell while the protein components are translated in the cytoplasm. The poxviruses represent the exception, as all macromolecular synthesis occurs cytoplasmically. Similar to the poxviruses, the viral components of most of the riboviruses are synthesized in the cytoplasm. But here, too, there are exceptions: nuclear synthesis of some viral macromolecules occurs in the Orthomyxoviridae (the group including influenza) and some of the Paramyxoviridae and Retroviridae.

Question 98

An intact virus is dissociated into nucleic acid and protein. Purification removes the nucleic acid and retains the protein. After such processing, which of the following structures or features is present in only some viruses? ## Footnote 1 capsid 2 a nucleic acid, either RNA or DNA, single- or double-stranded 3 envelope 4 nucleocapsid 5 protein coat

Answer 98

envelope ## Footnote The genome, which exists in all virions, may be RNA or DNA, single or double stranded. A protein coat, the capsid, encloses the genome of all viruses. The capsid is composed of several subunits, which exist in repeating patterns. Together, the genome and capsid are termed a nucleocapsid, so this structure is also present in the intact virion. The nucleocapsid structures have two common symmetries: helical and icosahedral. The paramyxoviruses, or homyxoviruses, and rhabdoviruses contain a nucleocapsid with helical symmetry, while adenovirus, iridovirus, papovavirus, parvovirus, picornavirus, and reovirus provide examples of the latter symmetry. Of the structures listed above, only the envelope is not present in all viruses; although, among the animal viruses, only 6 families lack this protective structure. The viruses, which are enveloped, contain a phospholipid bilayer coating, which they obtain from the host cell during budding through the cell membrane. Interestingly, the regions of the cell through which the virions bud are virally modified, such as to include the viral glycoprotein spikes. Among the exceptions are the host-encoded proteins of the herpesviruses, which are unmodified. In addition, the envelopes of the RNA tumor viruses may contain some proteins encoded by the host.

Question 99

An immunologist studying macrophages performs a series of experiments to study the pathophysiology and immunology of macrophages exposed to viral attack. Which of the following activities in macrophages is counterproductive for cellular defense against viral attack? ## Footnote 1 Phagocytic activity 2 Cytokine-initiated antiviral activity 3 Reduction of viral infection/replication in other cells 4 Antigen presentation 5 Virus reservoirs in mononuclear phagocytes

Answer 99

Virus reservoirs in mononuclear phagocytes ## Footnote Mononuclear phagocytes (MNPs), which consist of blood monocytes, tissue macrophages, and dendritic cells, are the main cellular elements responsible for elimination of viral pathogens. At the same time, MNPs are the targets and reservoirs for many viruses. Most noteworthy, the MNPs utilize phagocytosis as the first battle armament against the onslaught. This greatly diminishes the quantity of virus until other aspects of the immune system can be activated. Utilizing a number of antimicrobial mechanisms, macrophages can prevent infection or replication of the virus in other cells, representing an additional protection mechanism. Antibodies produced in response to viral infection may lead to either neutralization or lysis of the target cells. This is partially governed by the macrophage, functioning nonspecifically as an effector cell for antibody dependent cellular cytotoxicity. In addition, both macrophages and monocytes can either activate or be activated upon by cytokines to further increase their antiviral vigilance. The uptake, processing, and delivery of viral antigens to T cells in the lymph nodes referred to as antigen presentation rounds out the defense mechanisms utilized by macrophages. Monocytes and dendritic cells also function as antigen presenting cells.

Question 100

Influenza strains A, B, and C are examined for antigenic variation by an epidemiologist. Which of the following are consistent among the three influenza strains? ## Footnote 1 Hemagglutinin 2 Sialic acid binding site 3 M2 protein 4 M2 protein and hemagglutinin 5 Hemagglutinin and sialic acid binding site

Answer 100

Sialic acid binding site ## Footnote Antigenic variation among viruses is hardly uncommon. Nonetheless, only for the influenza viruses does this mutability have extreme epidemiological ramifications. Development of monoclonal antibody technology in recent years has dramatically increased the ability to identify such variations. Among the strains of influenza so far examined, the sialic acid binding site, which exist in a depression on the molecule, is uniquely constant. Hemagglutinin modulates the fusion between the virion and cell membrane and has 4 epitopes.

Question 101

Viruses may be cultivated in vitro in a number of cell systems or other biological entities. Among those viruses of viral groups listed below, which is best assayed by viral enzymes? ## Footnote 1 Influenza 2 Parainfluenza 3 Mumps virus 4 Hepatitis B virus 5 Retroviridae

Answer 101

Hepatitis B virus ## Footnote No suitable cell culture system is currently available for the hepatitis B virus, making the task of assaying especially challenging. Fortunately, the hepatitis B virus produces a DNA dependent polymerase, which is virus-specific. Influenza A, influenza B, mumps virus, and parainfluenza virus may be cultured in primary monkey kidney cells. Influenza A, B, and C all may be cultured in eggs. Influenza A and B may be detected by hemadsorption, cytopathic effect, and hemagglutination; Influenza C by hemagglutination. Retroviridae may be cultured in T lymphocytes with methods of detection of transformation, reverse transcriptase, cytopathic effect, or immunofluorescence.

Question 102

A basic scientist at a medical school is interested in evaluating a mouse for exposure to a virus. Several samples of tissues and cells are taken for analysis. Which of the following methods for assessing viral exposure is based on an indirect measurement? ## Footnote 1 Detection of viral DNA or RNA in cells, serum, or tissues 2 Detection of antiviral antibodies in the blood or tissues 3 Detection of intracellular viral antigens 4 Detection of virus particles 5 Visualization of virions by electron microscopy

Answer 102

Detection of antiviral antibodies in the blood or tissues ## Footnote Direct methods of detection measure the virus particles themselves, either by immunoassay methods, visualization, or molecular techniques. Initially, the detection of either DNA or RNA required a high titer of virus. With the availability of the polymerase chain reaction (PCR) or reverse transcription PCR (RTPCR), this limitation should theoretically no longer exist. Clearly, the detection of antibodies against the etiological agent represents an indirect method of assessing viral exposure, since the immune response to the etiological agent is detected rather than the agent itself. Infected tissues may contain fluorescent- or peroxidase-labeled antibodies.

Question 103

A virologist in a microbiology department of a medical school studies the ability of DNA and RNA viruses to transform cells in animals and cell cultures. Which DNA virus in the following list does not show transforming ability in either animals or cell cultures? ## Footnote 1 Retroviruses 2 Hepatitis B virus 3 Parvovirus 4 Epstein-Barr virus 5 Papillomavirus

Answer 103

Parvovirus ## Footnote Of all of the DNA viruses, only the single-stranded parvoviruses do not exhibit transformation potential in animals or cell cultures. Although the retroviruses do transform cells, they are RNA viruses. Interestingly, only these RNA viruses utilize a DNA template in their replication. The hepatitis B virus (HBV), dispersed throughout the blood and liver of patients with serum hepatitis, is capable of causing hepatocellular carcinoma. Both HBV and retroviruses exhibit integration into the host DNA sequences. The Epstein-Barr virus, one of the herpes viruses, can cause Burkitt's lymphoma and nasopharyngeal carcinoma. Papillomavirus causes not only benign warts, but also alimentary carcinomas.

Question 104

A molecular virologist uses a variety of molecular biology methodologies to study viral pathogenies. In viral pathogenesis of cells, which of the following processes is caused directly by the synthesis of viral constituents? ## Footnote 1 Direct toxicity produced by virions 2 Inhibited cellular synthesis 3 Inhibited mitosis 4 Development of viral inclusion bodies 5 Increased mitosis

Answer 104

Development of viral inclusion bodies ## Footnote Cellular injury or death resulting from viral pathogenesis may occur as a consequence of toxicity, caused by the virus particles themselves. Other effects on the host cell may be due to altered cellular processes. For instance, the inhibition of cellular synthesis arises directly from the presence of virally encoded proteins. Also, the inhibition of mitosis in host cells results from chromosomal aberrations. The accumulation of newly synthesized viral constituents within the cell results in inclusion bodies. These have the potential to kill the cell as a consequence of their interference with cell processes.

Question 105

A microbiologist specializes in the pathophysiology of influenza. As both a clinician and research physician, she studies the molecular aspects of viral pathogenesis, as well as the structure of the virions themselves. Which of the following statements regarding influenza is most accurate? ## Footnote 1 The gastrointestinal tract is the primary target of the virus. 2 The virus may be not be detected by microscopy or immunoassay. 3 Influenza belongs to the Paramyxoviridae family of viruses. 4 Virions lack an envelope. 5 A spherical or pleomorphic appearance of the virions is possible.

Answer 105

A spherical or pleomorphic appearance of the virions is possible. ## Footnote Influenza viruses A and B, which produce a viral pneumonia or hemorrhagic pneumonia, belong to the Orthomyxoviridae family of viruses. The Paramyxoviridae family includes the measles virus, which can also cause pneumonia. Direct detection of the virus may be via electron microscopy, where the virions are enveloped, helically symmetrical, 80-170 nm in diameter, and either spherical or pleomorphic. Alternatively, the virus may be detected via immunoassay, primarily using antibodies that are labeled with either a fluorescent or peroxidase indicator.

Question 106

A cell biologist specializing in the study of cells bearing FC receptors performs an experiment to study in vitro viral pathogenesis. Cells are grown in 24 well cell culture dishes and infected with a 10 multiplicity of infection. Which of the following effects of antibodies appears unlikely, but is possible, upon viral exposure of cells bearing Fc receptors? ## Footnote 1 Viral neutralization 2 Enhanced viral entry due to opsonization 3 Viral growth enhancement 4 Apoptosis 5 Cell fusion

Answer 106

Enhanced viral entry due to opsonization ## Footnote Numerous antibodies are produced by the humoral immune system in response to viral infection. Antiviral antibodies may neutralize viruses by preventing their attachment and entry into the host cell after binding to the proteins of either the envelope or capsid. However, not all of the resultant antibodies exhibit antiviral activity. Amazingly, not only are some of the resultant antibodies inactive, some even enhances infection in vitro, an effect termed antibody dependent enhancement. Some members of the following families of viruses exhibit this phenomenon: Togaviridae, Reoviridae, Rhabdoviridae, Poxviridae, Bunyaviridae, Coronaviridae, Flaviviridae, Herpesviridae, and Lentiviridae. Opsonization, the process by which pathogens are coated with specific IgG antibody, enhancing their rate of phagocytosis via the Fc gamma receptors, is a phenomenon which may be encountered upon invasion with several different foreign entities, including, but not limited to, viruses and bacteria. Although viral particles may be cleared with greater efficiency following opsonization, opsonizing antibodies may increase the invasion of cells bearing Fc receptors. Apoptosis is not an unexpected result of viral infection of cells. Influenza virus and human immunodeficiency virus are common examples of virally induced apoptosis. Moreover, antibodies are not directly involved in virus-induced apoptosis. Cell fusion, resulting in the formation of giant syncytia, is an expected result of infection of cells with certain paramyxoviruses or herpesviruses. The fusion appears to be the result of induced changes in cell membranes through interaction of particular glycoproteins in viral envelopes. Fc receptors on cells are involved in immunoreactions rather than the cell fusion that leads to the formation of giant syncytia.

Question 107

A molecular virologist specializing in the interaction of viruses with cell surfaces and receptors. Which of the following statements accurately describes an interaction of viruses with cells? ## Footnote 1 Epstein-Barr virus binds only to T cells 2 Rhinovirus binds to epithelial cells in the airway 3 Human immunodeficiency virus type 1 binds to B cells 4 Poliovirus infects only the spinal cord's anterior horn cells 5 No cells actively phagocytize viruses

Answer 107

Rhinovirus binds to epithelial cells in the airway ## Footnote Epstein-Barr virus binds to the type-2 complement receptor of B cells. The specific molecule to which the rhinovirus binds is the intercellular adhesion molecule, which is expressed on the epithelial cells of the airway and on other cells as well. Human immunodeficiency virus type 1 binds to the CD4 molecule of T cells. While human poliovirus infection of the spinal cord's anterior horn cells can produce poliomyelitis, infection of cells in the gut and nasopharynx is also possible. Among the various means by which viruses may enter cells is the specific phagocytosis of viruses, termed viropexis.

Question 108

A mouse is exposed to an aerosol of influenza X31, a murine stain of influenza. Blood samples are collected at various time points following the exposure to the virus. The samples are centrifuged to pellet the red blood cells. The plasma is analyzed for antibody levels using an ELISA. Which of the following antibody responses first emerges upon infection with influenza? ## Footnote 1 IgG 2 IgM 3 IgA 4 IgE 5 IgG and IgA 6 IgA and IgE 7 IgG and IgE

Answer 108

IgM ## Footnote Among the major classes of immunoglobulin to appear upon infection with influenza virus, IgM appears first, and peaks during the second week after initial exposure. Not surprisingly, the appearance of IgM as the primary immunoglobulin also occurs with infection by other viruses. Both IgG and IgA appear in another two weeks. Additionally, reinfection results in the production of both IgG and IgA immunoglobulins. The viral antigens against which antibodies are directed include hemagglutinin, neuraminidase, nucleoprotein, and the M protein. IgE is the antibody class associated with the allergic response.

Question 109

A researcher specializing in systematics of viruses tabulates data from several epidemiological studies. The data she receives include the names of the individual viruses, the families to which they belong, the type of genome, presence of an envelope, the morphology of the virion, and which viruses are related to each other. Which of the following families contains the influenza virus? ## Footnote 1 Orthomyxoviridae 2 Paramyxoviridae 3 Coronaviridae 4 Picornaviridae 5 Rhabdoviridae

Answer 109

Orthomyxoviridae ## Footnote All of the families mentioned are RNA viruses. The Picornaviridae family contains viruses that lack an envelope and are icosahedral (rather than helical) in morphology. The Picornaviridae family contains enterovirus, cardiovirus, and rhinovirus. The Orthomyxoviridae family contains the influenza virus, while the Paramyxoviridae family contains the parainfluenza virus. The Rhabdoviridae and Coronaviridae families contain the rabies virus and Coronaviruses, respectively.

Question 110

An epidemiologist studies virology data including the names of virus families and the nature of the genome. Which of the following families contain RNA viruses? ## Footnote 1 Parvoviridae 2 Adenoviridae 3 Reoviridae 4 Herpesviridae 5 Poxviridae

Answer 110

Reoviridae ## Footnote Except for the Reoviridae, which contains the orbiviruses, rotaviruses, and reoviruses, all of the families mentioned are DNA viruses. The Parvoviridae and Adenoviridae families contain the Parvovirus and Adenovirus, respectively. The viruses in both of these families have a naked virion (i.e., without an envelope), but viruses in the former family have a complex nucleocapsid structure, while those in the latter family have an icosahedral nucleocapsid symmetry. The herpes simplex virus, cytomegalovirus, Varicella-Zoster virus, and the Epstein-Barr virus all belong to the Herpesviridae family. The family of Poxviridae contains complex viruses with a naked virion, such as the vaccinia, smallpox, and variola viruses.

Question 111

A study of various techniques to count infective virus particles is undertaken by a virologist. Among the methods for enumerating these inactive virions are the pock assay, plaque or focal assay, electron microscopy, and quantal assay. Which of the following methods is the most precise universally useful technique for enumerating infective virus particles? ## Footnote 1 Pock assay 2 Plaque or focal assay 3 Electron microscopy 4 Quantal assay 5 Flow cytometry

Answer 111

Plaque or focal assay ## Footnote The keys to this question are the terms "universally useful" and "infective." Some of the described methods lead to the counting of both viable and nonviable particles, as described below. Electron microscopy is useful for enumerating purified virus particles present at high density. The addition of a known number of latex particles to the suspension, followed by the calculation of the ratio of those particles to viral particles provides an accurate count. Of course, this technique has the disadvantage that viable and nonviable particles cannot be differentiated. Equally important, very few diagnostic laboratories, and indeed not all research laboratories, have ready access to an electron microscope. The plaque assay is the most precise measure of infectivity. The basis of this technique is the formation of clear zones, plaques, or foci in a monolayer of host cells. Serial dilutions of the virus are added to a monolayer of cells known to be infected by the cells (for example MDCK cells are used for influenza). Most commonly, after the virus has been allowed to absorb onto the cells, an agar overlay is added to prevent dispersion of the virus. This ensures that each plaque represents only a single initial virus particle. For viruses, which only infect contiguous cells without releasing virions into the surrounding medium, the agar may be replaced by a liquid. Certainly not applicable for all viruses, the pock assay involves the counting of localized lesions (pocks) that form on the chorioallantoic membrane (CAM) of the embryonated egg upon addition of known dilutions of the virus. As in the plaque assay, each lesion represents a single original virus particle. Instead of providing a quantitative measure of viral infectivity, quantal assays provide only a "yes or no" result. In quantal assays, each viral replication cycle results in an amplification of the effects of each individual virus particle. The virus is serially diluted, and appropriate cells are incubated with a known volume of each dilution. The endpoint for these assays may be negative effects, including morbidity in animals and development of lesions on either the chorioallantoic membrane or on the embryo of eggs. Following the incubation period, each target animal or sample is examined for a +/- response. Flow cytometry is used to enumerate cells, especially mammalian cells, rather than virus particles.

Question 112

A 27-year-old woman presents to her primary care provider with upper respiratory symptoms. An examination of throat swabs and stool specimens indicates the presence of virus particles. Examination of throat swabs and stool specimens is appropriate when, which of the following viruses is suspected? ## Footnote 1 Parainfluenza 2 Enterovirus 3 Papovavirus 4 Cytomegalovirus 5 Influenza

Answer 112

Enterovirus ## Footnote Among the respiratory viruses that can be isolated from throat secretions are influenza, parainfluenza, respiratory syncytial virus, and rhinovirus. These may also be present in nasal washes, nasopharyngeal swabs, lung biopsy, and aspirates of the lower respiratory tract. Additional respiratory viruses, which may be isolated from the stool in addition to the aforementioned locations, are the enterovirus and adenovirus. Certain viruses, which affect the central nervous system, may be isolated from throat swabs, including enterovirus. Cytomegalovirus and herpes simplex viruses are among the viruses, which also can cause CNS illness. These two also cause congenital or perinatal exanthem, in which case isolation may be made from throat swabs.

Question 113

An in vitro experiment is performed to study viral pathogenesis of monocytes infected with multiple viruses. Macrophages derived from monocytes were co-infected with human immunodeficiency virus (HIV) and one of the following viruses: herpes simplex virus, cytomegalovirus, or Epstein-Barr virus. The coinfection of monocytes with both HIV and which of the following viruses results in enhanced production of virus? ## Footnote 1 Herpes simplex virus 2 Cytomegalovirus 3 Epstein-Barr virus 4 Influenza A 5 Influenza B

Answer 113

Cytomegalovirus ## Footnote Co-infection of HIV-infected or HIV-susceptible individuals with other viruses is quite common. Among the viruses involved in these secondary infections are cytomegalovirus, herpes simplex virus, and Epstein-Barr virus. Of particular interest, there is at least a five-fold increase in HIV production in the first three weeks of culture. Macrophages and monocytes do not support active replication of influenza viruses.

Question 114

A virologist specializing in systematics, the study of relatedness of organisms, analyzed data from several studies. Which of the following pairs of viruses are most closely related? ## Footnote 1 Poliovirus and orbivirus 2 Enteroviruses and rotavirus 3 Rotavirus and echoviruses 4 Enteroviruses and rhinoviruses 5 Rhinoviruses and orbivirus

Answer 114

Enteroviruses and rhinoviruses ## Footnote Both the enterovirus group (which includes the poliovirus, coxsackieviruses, and echoviruses), and the Reoviridae, (which includes the reovirus, orbivirus, and rotavirus), have an RNA genome. The genomes of the enterovirus group are linear and single-stranded, whereas those of the Reoviridae are double-stranded and may be either linear or segmented. The Picornaviridae family of viruses contains the enterovirus and the rhinoviruses, which have numerous properties in common with each other. Viruses of this family lack an envelope, and are icosahedral, with a diameter of 20nm. The genome is a single-strand RNA. The enteroviruses are stable to acid, while the rhinoviruses are acid-sensitive.

Question 115

A microbiologist specializing in virology analyzes biochemical and structural characteristics of viruses belonging to the Retroviridae, Togaviridae, paramyxoviruses, Coronaviridae, and Rhabdoviridae families. Which of these families is structurally most closely related to the influenza virus? ## Footnote 1 Retroviridae 2 Togaviridae 3 Paramyxoviruses 4 Coronaviridae 5 Rhabdoviridae

Answer 115

Paramyxoviruses ## Footnote Each of these viral families or groups has an RNA genome and envelope. The paramyxoviruses are structurally the most closely related to influenza, since both are negative sense RNA viruses and many of the paramyxoviruses contain a neuraminidase and hemagglutinin. There are some notable differences, however. In the paramyxoviruses, both neuraminidase and hemagglutinin functions are accomplished by a single glycoprotein on one type of spike, whereas in influenza, these functions are accomplished by two separate glycoproteins that are present on two types of spikes. A notable exception, however, is influenza C, which has both functions on a single glycoprotein. In addition, the genome is segmented in influenza, but not in the paramyxoviruses. The viruses in the Togaviridae and Coronaviridae families differ from the influenza viruses in that they have a positive sense RNA genome. Viruses in the Rhabdoviridae family, which includes the vesicular stomatitis virus and the rabies virus, are bacilliform negative-stranded RNA viruses.

Question 116

A 45-year-old HIV positive man comes in for a routine physical. He says he feels well and has no complaints. His physical exam reveals swollen lymph nodes in the neck and axilla. The rest of his exam is WNL. What immunity is most likey to be deficient with these symptoms and at this stage during his disease process? ## Footnote 1 Humoral 2 Cell-mediated 3 Complement system 4 Phagocytic dysfunction 5 Autoimmunity

Answer 116

Cell-mediated ## Footnote Your patient is most probably in the clinically asymptomatic stage of HIV infection. In this stage, CD4 expresses cells (macrophages, T-helper lymphocytes, monocytes, dendritic cells) are infected, but not destroyed. Therefore, in this stage, cell-mediated immunity is deficient. Cell-mediated immunity involves the activation of macrophages, natural killer cells, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. Humoral immunity depends on the activation of B-lymphocytes and plasma cell production of immunoglobulins. Immature B cells can be activated in a T cell dependent or T cell independent way. Once helper T cell function fails, humoral immunity starts to decline. This happens later in the disease process, when immune system loses its ability to improve the affinity of their antibodies (mainly IgG and IgA) and even becomes unable to generate B cells. The complement system is the mediator of the humoral immune response. It enables the body to react to an infective agent like HIV via inflammation, localization and inactivation. Macrophages and neutrophils are the main effectors of nonspecific immunity because they present antigens of both conventional and opportunistic microorganisms they phagocytize to T lymphocytes. HIV infection significantly increases a patient’s susceptibility to common pathogens and opportunistic infections. This increased susceptibility is related to abnormal antibody response to specific antigens, while the occurrence of opportunist infections is associated with mononuclear phagocyte system dysfunction. Both happen in later stages of HIV infection. Autoimmunity is the failure of an organism in recognizing its own constituent parts as self, which allows an immune response against its own cells and tissues. The maintenance of self-tolerance is depleted in active HIV infection and the number of autoimmune diseases increases.

Question 117

Refer to the image. The 26-year-old male seen in the image is HIV positive with a CD4 count less than 200. While he was in the hospital for the treatment of his miliary Tb, he developed smooth, skin-colored, umbilicated papules on his face. The lesions are asymptomatic but spreading gradually to the other parts of the body and causing cosmetic problems to the patient. What is the name of this skin infection? ## Footnote 1 Verrucae vulgaris 2 Filiform warts 3 Condyloma acuminata 4 Kaposi's sarcoma 5 Molluscum contagiosum

Answer 117

Molluscum contagiosum ## Footnote Molluscum contagiosum is a poxvirus infection characterized by skin-colored, smooth, waxy, umbilicated papules 2 to 10 mm in diameter. Transmission can be direct or venereal. Its contagiousness to others varies. The lesions may be seen anywhere on the skin, face, body, or genital area. They are usually asymptomatic unless secondarily infected. This disease is quite common in children, and the lesions can be widespread in patients with reduced cellular immunity. Verrucae vulgaris is the other name for common warts. They are sharply demarcated, rough-surfaced, round, irregular, light gray, yellow, brown, or grayish black lesions. Filiform warts are long, narrow, small growths of skin, usually seen on the eyelids, face, neck, or lips. Condyloma acuminata is the name for genital warts. They are moist, soft, pink, or red swellings that grow rapidly and become pedunculated. They most commonly occur on warm, moist surfaces in the subpreputial area, perineum, vaginal wall, cervix, penile shaft in men, and urethral meatus. Kaposi's sarcoma is a vascular skin tumor associated with AIDS. They may be the first notable manifestation of AIDS. The lesions start as pink or red papules, round or oval, and appear first on the upper body and mucosa. They may become widely disseminated on the skin and are associated with organ and lymph node involvement. This patient does not have the typical Kaposi's sarcoma lesions.

Question 118

Case The 26-year-old HIV-positive man has a CD4 count <200. While he was in the hospital for the treatment of his miliary Tb, he developed smooth skin-colored umbilicated papules on his face. The lesions are asymptomatic, but they are spreading gradually to other parts of the body and causing cosmetic problems to the patient. What organism is the most likely cause of this skin infection? ## Footnote 1 Poxvirus 2 Human papillomavirus 1 3 Parvovirus B19 4 Herpes simplex virus type I 5 Ebstein-Barr virus

Answer 118

Poxvirus ## Footnote This patient has typical lesions of Molluscum contagiosum, a poxvirus infection characterized by skin-colored smooth waxy umbilicated papules 2-10 mm in diameter. Transmission can be direct or venereal. Its contagiousness to others varies. The lesions may be seen anywhere on the skin, face, body or genital area. They are usually asymptomatic unless secondarily infected. This disease is quite common in children, and the lesions can be widespread in patients with reduced cellular immunity. Human papillomavirus 1 causes skin or plantar warts on the hands or feet. These warts typically do not present on the face. Parvovirus B19 is the cause of erythema infectiosum (slapped-cheek disease, fifth disease). This rash is erythamatous with surrounding pallor that presents on the cheeks. Herpes simplex virus type I causes acute gingivostomatitis, recurrent herpes labialis (cold sores), keratoconjunctivitis, and encephalitis. The description of the umbilicated painless lesions above are not classic features of herpatic lesions. Ebstein-Barr virus is the cause of infectious mononucleosis. Acute EBV infection does not present with a rash, but a rash can develop after the administration of amoxicillin.

Question 119

The virus responsible for causing AIDS (HIV) is classified as a retrovirus. A retrovirus contains an RNA molecule and a protein that is required for the replication of the virus. This required protein is classified as a ## Footnote 1 Protease 2 Histone 3 Telomerase 4 DNA polymerase 5 Reverse transcriptase

Answer 119

Reverse transcriptase ## Footnote A retrovirus is an infectious particle consisting of an RNA genome packaged in a protein capsid, surrounded by a lipid envelope. This lipid envelope contains polypeptide chains, including receptor-binding proteins that link to the membrane receptors of the host cell, initiating the process of infection. In order to replicate, its genetic material (RNA) must first be converted to a DNA molecule by the enzyme reverse transcriptase. This enzyme, which is found in the virus particle, is a DNA polymerase that uses an RNA molecule as a template to synthesize DNA, resulting in an RNA/DNA double helix. Further enzyme action leads to the synthesis of a DNA double helix using the RNA/DNA template. This DNA helix can then integrate into the host chromosome and be transcribed into RNA molecules coding for capsid proteins, envelope proteins, and the reverse transcriptase. This integration into the host DNA is carried out by the viral integrase. Integration into the host chromosome is required for the synthesis of new viral RNA molecules. A host cell RNA polymerase is responsible for this transcription. Many new virus particles are then assembled containing the RNA molecule and the enzyme reverse transcriptase.

Question 120

The virus responsible for causing AIDS (HIV) is classified as a retrovirus. Many of the drugs used to treat HIV infection take advantage of a unique sequence of events involved in the replication of retroviruses. In order for HIV to replicate, which of the following steps must occur first? ## Footnote 1 The viral RNA must be converted to DNA 2 The viral RNA must be degraded 3 New viral RNA molecules must be synthesized by the viral RNA polymerase 4 The host cell must synthesize reverse transcriptase 5 A DNA polymerase must be synthesized from the RNA template

Answer 120

The viral RNA must be converted to DNA ## Footnote A retrovirus is an infectious particle consisting of an RNA genome packaged in a protein capsid, surrounded by a lipid envelope. This lipid envelope contains polypeptide chains, including receptor-binding proteins that link to the membrane receptors of the host cell, initiating the process of infection. In order to replicate, its genetic material (RNA) must first be converted to a DNA molecule by the enzyme reverse transcriptase. This enzyme, which is found in the virus particle, is a DNA polymerase that uses an RNA molecule as a template to synthesize DNA, resulting in an RNA/DNA double helix. Further enzyme action leads to the synthesis of a DNA double helix using the RNA/DNA template. This DNA helix can then integrate into the host chromosome and be transcribed into RNA molecules coding for capsid proteins, envelope proteins, and the reverse transcriptase. This integration into the host DNA is carried out by the viral integrase. Integration into the host chromosome is required for the synthesis of new viral RNA molecules. A host cell RNA polymerase is responsible for this transcription. Many new virus particles are then assembled containing the RNA molecule and the enzyme reverse transcriptase.

Question 121

Case A 20-year-old pregnant woman presents at 21 weeks’ gestation with symptoms and signs of preeclampsia. Her symptoms have been present for the past 2 days. Prior to that, she had flu-like symptoms and a lace-like rash on her trunk and extremities and a flushed face. Intrauterine fetal demise was detected by ultrasonogram. Labor was induced, and a stillborn male fetus was delivered. Serum was collected for viral titers of the suspected agent that had caused the patient’s flu-like symptoms and fetal demise. The viral IgM titers were positive, as suspected. What is the most likely offending agent? ## Footnote 1 Herpes simplex type 1 2 Herpes simplex type 2 3 Epstein-Barr virus 4 Cytomegalovirus 5 Varicella-zoster 6 Parvovirus B19

Answer 121

Parvovirus B19 ## Footnote Parvovirus B19 is a member of the family Parvoviridae and is the causative agent of erythema infectiosum (fifth disease). The hallmark symptom of erythema infectiosum is a mild rubella-like erythematous rash that produces arthropathy, especially in women. The disease has two separate components. The first component is the lytic phase where the lytic action of the virus replication in erythroid precursors gives rise to a transient arrest of erythrocytic production. This can result in a slight drop in hemoglobin. Hemoglobin levels will substantially drop in those patients with chronic hemolytic anemia. This is the viremic stage, and mild flu-like symptoms with pyrexia and chills are not uncommon. These flu-like symptoms can last for 1 to 3 days. One week after the viremia peak, the second phase occurs where the virus is rarely detectable. The second phase is where the erythematous maculopapular rash and arthropathy occur. The characteristic rash produces a lace-like appearance on the trunk and extremities and a “slapped-cheek” appearance on the face. Erythema infectiosum infections in pregnant women can induce fetal loss (5-20%), especially if the infection occurs at less than 20 weeks. Herpes simplex type 1 (HSV-type 1) belongs to the family Herpesviridae and causes an infection that characteristically presents as an eruption of vesicles that are restricted to areas around the mouth, lips, and nostrils. The infection can also occur in the genital area, thought HSV-type 2 is more commonly associated with genital infections, called herpes labialis. Patients usually can predict the onset of an eruption due to a prodromal stage of itching or other sensations that can occur a few hours to a few days prior to the eruption of vesicles. HSV-type 1 also causes primary infections of the oral mucous membranes in children and herpetic eye infections. Eruptions can occur at any time and depend on the immunological status of the host, health, and various other factors that vary from host to host. Herpes simplex type 2 (HSV-type 2) belongs to the family Herpesviridae and causes an infection that characteristically presents as an eruption of vesicles that are restricted to areas around the genital area. Multiple vesicles in females appear on the vulva, in the vagina, and on the portio. Multiple vesicles in men are found often on the sulcus of the glans and the preputium but can be found on any part of the penis. Duration and severity of the eruptions are usually more severe in females than in males. HSV-type 1 can also be found to cause genital eruptions but at a significantly lower rate. HSV-type 2 causes 75% of all neonatal herpes (a severe complication of genital HSV infection) where the newborn acquires the virus by contamination through the birth canal. Eruptions can occur at any time and depend on the immunological status of the host, health, and various other factors that vary from host to host. Epstein-Barr virus belongs to the family Herpesviridae and is the causative agent of infectious mononucleosis (IM), Burkitt's Lymphoma, and undifferentiated nasopharyngeal carcinoma. IM characteristically produces a marked lymphocytosis involving almost all of the lymphoreticular tissues. This leads to hepatomegaly, splenomegaly, lymphadenopathy, and lymphoid hyperplasia of the oronasopharynx. The peripheral blood smear contains atypical lymphocytes of the Downey II type. It is generally a self-limiting disease; however, it can cause a severe protracted illness that can at times prove to be fatal. Patients with an unusual immuno-defect known as the X-linked lymphoproliferative syndrome frequently have overwhelming EBV primary infections, which can be fatal in the majority of the cases. Cytomegalovirus (CMV) belongs to the family Herpesviridae and causes cytomegalovirus mononucleosis, cytomegalic inclusion disease, and cytomegalovirus infection in the immunocompromised. CMV resembles infectious mononucleosis in that atypical lymphocytosis, fever, and malaise are characteristic symptoms to both. Pharyngitis is present as a symptom, though less severe in CMV than in infectious mononucleosis. The heterophile antibody test is also negative in CMV. Toxoplasmosis may also mimic CMV and infectious mononucleosis and thus must be considered in the differential diagnosis in those patients with a negative heterophile antibody test and mono-like symptoms. Transmission of CMV from mother to fetus may occur at any time during the pregnancy. Fetal loss is less likely than congenital CMV infection, which – in its most severe form – is manifested as hepatosplenomegaly, microcephaly, chorioretinitis, hearing loss, and thrombocytopenia. The mortality rate is high. Varicella-zoster virus is a member of the family Herpesviridae and is the causative agent of Varicella (chickenpox) and herpes zoster (shingles). Varicella is highly communicable in children. Varicella usually has an acute onset with fever and a progressive rash that leads to the formation of vesicles. These vesicles eventually crust over. They can form on the mucous membranes of the mouth (most commonly the palate area), as well as on the skin. Cutaneous eruptions appear early and most profusely on areas of the back, abdomen, and chest. The palpebral conjunctiva, trachea, larynx, rectal, and vaginal mucosa may also become involved. In adults, older children, and children with primary immunodeficiency or deficient cell-mediated immunity, the infection is more severe than in healthy children. Fevers are usually more prolonged in duration and higher; the rash is more profuse; constitutional symptoms are more severe; and complications are often more common. Varicella infection acquired during pregnancy tends to be associated with a high degree of morbidity and mortality, which can be reduced with supportive medical care. Infection prior to 20 weeks’ gestation is associated with a relatively low risk of congenital anomalities but fetal ultrasound should be performed.

Question 122

Case An 18-year-old female sex worker presents to the emergency room with fever, shaking chills, and body aches which she attributes to the flu. Her body temperature is 38.9°C; pulse is 75/minute; and blood pressure is normal. One year previously, she had a documented case of a Neisseria gonorrhea that was treated, and two clinic examinations proved elimination of the infection. The patient mentions a painful genital region. Examination reveals lesions that are vesicular and ulcerative in appearance around the labia minora and majora. Specimens are obtained for HIV testing, Neisseria gonorrhea culture, viral culture, and Chlamydia culture. The HIV test was negative. Tzanck prep was ordered and was reported as positive. Based on the clinical findings, history, and Tzanck prep finding, what is the likely organism causing this patient’s symptoms? ## Footnote 1 Herpes simplex type 1 2 Herpes simplex type 2 3 Epstein-Barr virus 4 Cytomegalovirus 5 Varicella-zoster 6 Parvovirus B19

Answer 122

Herpes simplex type 2 ## Footnote Herpes simplex type 2 (HSV-type 2) belongs to the family Herpesviridae and causes an infection that characteristically presents as an eruption of vesicles that are restricted to the genital area. Multiple vesicles in females appear on the vulva and vagina. Multiple vesicles in men are found most often on the sulcus of the glans but can on any part of the penis. Duration and severity of the eruptions are usually more severe in females than in males. A direct smear prepared from the base of a suspected lesion and stained by either Giemsa or Papanicolaou method may show intranuclear inclusions or multinucleated giant cells typical of herpes (Tzanck test). The Tzanck test is also positive in Herpes simplex type-1 and Varicella zoster virus infections but these rarely infections do not produce the characteristic presentation described in this scenario. Herpes simplex type 1 (HSV-type 1) belongs to the family Herpesviridae and causes an infection that characteristically presents as an eruption of vesicles that are restricted to areas around the mouth, lips, and nostrils. The infection is called herpes labialis. Patients usually can predict the onset of an eruption due to a prodromal stage of itching or other sensations that can occur a few hours to a few days prior to the eruption of vesicles. HSV-type 1 also causes primary infections of the oral mucous membranes in children and herpetic eye infections. Eruptions can occur at any time and depend on the immunological status of the host, health, and various other factors that vary from host to host. Varicella-zoster virus is a member of the family Herpesviridae and is the causative agent of Varicella (chickenpox) and herpes zoster (shingles). Varicella is highly communicable in children. Varicella usually has an acute onset with fever and a progressive rash that leads to the formation of vesicles. These vesicles eventually crust over. They can form on the mucous membranes of the mouth (most commonly the palate area), as well as on the skin. Cutaneous eruptions appear early and most profusely on areas of the back, abdomen, and chest. The palpebral conjunctiva, trachea, larynx, rectal, and vaginal mucosa may also become involved. In adults, older children, and children with primary immunodeficiency or deficient cell-mediated immunity, the infection is more severe than in healthy children. Fevers are usually more prolonged in duration and higher, the rash is more profuse, constitutional symptoms are more severe, and complications are often more common. Parvovirus B19 is a member of the family Parvoviridae and is the causative agent of erythema infectiosum (fifth disease). The hallmark symptom of erythema infectiosum is a mild rubella-like erythematous rash that produces a lace-like appearance on the trunk and extremities and a slapped cheek appearance on the face as well as prominent arthropathy, especially in women. The disease has 2 separate components. The first component is the lytic phase where the lytic action of the virus replication in erythroid precursors gives rise to a transient arrest of erythrocytic production. This can result in a slight drop in hemoglobin. Hemoglobin levels will substantially drop in those patients with chronic hemolytic anemia. This is the viremic stage, and mild flu-like symptoms with pyrexia and chills are not uncommon. These flu-like symptoms can last for 1 to 3 days. 1 week after the viremia peak, the second phase occurs where the virus is rarely detectable. The second phase is where the erythematous maculopapular rash and arthropathy occur. Erythema infectiosum infections in pregnant women can induce fetal loss (5-20%). Infection does not produce a positive Tzanck test. Epstein-Barr virus belongs to the family Herpesviridae and is the causative agent of infectious mononucleosis (IM), Burkitt's Lymphoma, and undifferentiated nasopharyngeal carcinoma. IM characteristically produces a marked lymphocytosis involving almost all of the lymphoreticular tissues. This leads to hepatomegaly, splenomegaly, lymphadenopathy, and lymphoid hyperplasia of the oronasopharynx. The peripheral blood smear contains atypical lymphocytes of the Downey II type. It is generally a self-limiting disease; however, it can cause a severe protracted illness that can at times prove to be fatal. Patients with an unusual immuno-defect known as the X-linked lymphoproliferative syndrome frequently have overwhelming EBV primary infections, which can be fatal in the majority of the cases. Infection does not produce a positive Tzanck test. Cytomegalovirus (CMV) belongs to the family Herpesviridae and causes cytomegalovirus mononucleosis, cytomegalic inclusion disease, and cytomegalovirus infection in the immunocompromised. CMV resembles infectious mononucleosis in that atypical lymphocytosis, fever, and malaise are characteristic symptoms to both. Pharyngitis is present as a symptom, though less severe in CMV than in infectious mononucleosis. The heterophile antibody test is also negative in CMV. Toxoplasmosis may also mimic CMV and infectious mononucleosis and thus must be considered in the differential diagnosis in those patients with a negative heterophile antibody test and mono-like symptoms. Infection does not produce a positive Tzanck test.

Question 123

Case A 3-year-old girl presents with a 3-day history of fever of 38.9°C, headache, and body aches. The patient appears irritable. Of significance is the presence of a rash that is vesicular, pustular, and crusted in various areas of the body. An examination of the throat reveals an absence of any redness or inflamed tonsils, but vesicles were noted on the lips and on the palate. There is no history of previous dermatologic disorder. A Group A Streptococcus screen test was negative. Results of a confirmatory throat culture were negative. Based solely on the clinical presentation, you can make a confident diagnosis. Serological tests are performed to confirm your diagnosis. Three days later, your diagnosis is confirmed. What is the probable agent causing disease in this child? ## Footnote 1 Herpes simplex type 1 2 Herpes simplex type 2 3 Epstein-Barr virus 4 Cytomegalovirus 5 Varicella-zoster 6 Parvovirus B19

Answer 123

Varicella-zoster ## Footnote Varicella-zoster virus is a member of the family Herpesviridae and is the causative agent of Varicella (chickenpox) and herpes zoster (shingles). Varicella is highly communicable in children. Varicella usually has an acute onset with fever and a progressive rash that leads to the formation of vesicles. These vesicles eventually crust over. They can form on the mucous membranes of the mouth (most commonly the palate area), as well as on the skin. Cutaneous eruptions appear early and most profusely on areas of the back, abdomen, and chest. The palpebral conjunctiva, trachea, larynx, rectal, and vaginal mucosa may also become involved. The infection is more severe in adults, older children, and children with primary immunodeficiency or deficient cell-mediated immunity than it is in healthy children. Fevers are usually more prolonged in duration and higher, the rash is more profuse, constitutional symptoms are more severe, and complications are often more common. Parvovirus B19 is a member of the family Parvoviridae and is the causative agent of erythema infectiosum (fifth disease).The hallmark symptom of erythema infectiosum is a mild rubella-like erythematous rash that produces arthropathy, especially in women. The disease has 2 separate components. The first component is the lytic phase where the lytic action of the virus replication in erythroid precursors gives rise to a transient arrest of erythrocytic production. This can result in a slight drop in hemoglobin. Hemoglobin levels will substantially drop in those patients with chronic hemolytic anemia. This is the viremic stage, and mild flu-like symptoms with pyrexia and chills are not uncommon. These flu-like symptoms can last for 1 to 3 days. One week after the viremia peak, the 2nd phase occurs where the virus is rarely detectable. The 2nd phase is when the erythematous maculopapular rash and arthropathy occur. Erythema infectiosum infections in pregnant women can induce fetal loss (5 - 20%). Herpes simplex type 1 (HSV-type 1) belongs to the family Herpesviridae and causes an infection that characteristically presents as an eruption of vesicles that are restricted to areas around the mouth, lips, and nostrils. The infection can also occur in the genital area, though HSV-type 2 is more commonly associated with genital infections, called herpes labialis. Patients usually can predict the onset of an eruption due to a prodromal stage of itching or other sensations that can occur a few hours to a few days prior to the eruption of vesicles. HSV-type 1 also causes primary infections of the oral mucous membranes in children and herpetic eye infections. Eruptions can occur at any time and depend on the immunological status of the host, health, and various other factors that vary from host to host. Herpes simplex type 2 (HSV-type 2) belongs to the family Herpesviridae and causes an infection that characteristically presents as an eruption of vesicles that are restricted to areas around the genital area. Multiple vesicles in woman appear on the vulva, in the vagina, and on the portio. Multiple vesicles in men are found often on the sulcus of the glans and the preputium but can be found on any part of the penis. Duration and severity of the eruptions are usually more severe in girls/women than in boys/men. HSV-type 1 can also be found to cause genital eruptions but at a significantly lower rate. HSV-type 2 causes 75% of all neonatal herpes (a severe complication of genital HSV infection) where the newborn acquires the virus by contamination through the birth canal. Eruptions can occur at any time and depend on the immunological status of the host, health, and various other factors that vary from host to host. Epstein-Barr virus belongs to the family Herpesviridae and is the causative agent of infectious mononucleosis (IM), Burkitt's Lymphoma, and undifferentiated nasopharyngeal carcinoma. IM characteristically produces a marked lymphocytosis involving almost all of the lymphoreticular tissues. This leads to hepatomegaly, splenomegaly, lymphadenopathy, and lymphoid hyperplasia of the oro-nasopharynx. The peripheral blood smear contains atypical lymphocytes of the Downey II type. It is generally a self-limiting disease, but it can cause a severe protracted illness that can at times prove to be fatal. Patients with an unusual immuno-defect known as the X-linked lymphoproliferative syndrome frequently have overwhelming EBV primary infections, which can be fatal in the majority of the cases. Cytomegalovirus (CMV) belongs to the family Herpesviridae and causes cytomegalovirus mononucleosis, cytomegalic inclusion disease, and cytomegalovirus infection in the immunocompromised. CMV resembles infectious mononucleosis in that atypical lymphocytosis, fever, and malaise are characteristic symptoms to both. Pharyngitis is present as a symptom, though less severe in CMV than in infectious mononucleosis. The heterophile antibody test is also negative in CMV. Toxoplasmosis may also mimic CMV and infectious mononucleosis, so it must be considered in the differential diagnosis in those patients with a negative heterophile antibody test and mono-like symptoms.

Question 124

Case A 42-year-old female IV drug user experiences vague symptoms consisting of fatigue, aches and pains, and nausea. She has developed a distaste for her cigarettes. She appeared jaundiced for a few days, but the condition spontaneously resolved. She goes to the free clinic and they run preliminary blood tests. The staff at the free clinic tell the patient she does not have hepatitis B. What may be present in this patient's lab work to indicate she may be in the window period? Answer Choices ## Footnote 1 Anti-HBc 2 HBsAg 3 Anti-HBe 4 HBeAg 5 Anti-HBs

Answer 124

Anti-HBc ## Footnote Hepatitis B is transmitted by exposure to blood or blood products. If she shared needles when using IV drugs, she has put herself at risk for infection with hepatitis B. The window is the period in which HBsAg (HBV surface antigen) is not detectable. Although anti-HBs (antibody to HBV surface antigen) are present, they are actively bound to HBsAg and are therefore not detectable. During the window period of a hepatitis B infection, the only marker present would be IgM anti-HBc (antibody to HBV core antigen); the window period is also referred to as the core window. HBsAg (HBV surface antigen) is the first serological marker to appear in hepatitis B infection. After HBsAg is cleared from the serum, the patient is in the window period. Anti-HBs (antibody to HBV surface antigen) is seen at the end of infection. The appearance of anti-HBs marks the end of the window period. The presence of anti-HBs gives a patient immunity. HBeAg (HBV "e" antigen) can be seen with acute hepatitis. It is a marker for infectivity. Anti-HBe (antibodies to Hepatitis B envelope) is present early in the infection.

Question 125

The human immunodeficiency virus (HIV) shows extensive genetic variation and undergoes rapid evolution. The rapid replication of HIV, coupled with genetic variability, leads to the generation of many variants of HIV in a single infected patient in the course of an infection. Thus HIV can rapidly develop resistance to antiviral drugs. When antiviral drugs are administered, variants of the virus that carry mutations conferring resistance to their effects emerge and expand until former levels of plasma virus are regained. Resistance to some of the protease inhibitors appears after only a few days. This remarkable variability was first recognized in HIV, has since proved to be common to the other lentiviruses. What is it caused by? ## Footnote 1 Gene conversion 2 Hypermutability 3 Gene duplication 4 Antigenic shift 5 Antigenic drift

Answer 125

Hypermutability ## Footnote Within the retrovirus family, HIV is classified as a lentivirus, having genetic and morphological similarities to animal lentiviruses, examples of which are listed in the table. Refer to the table. Virus Host Primary cell type affected Human immunodeficiency virus (HIV) Human T lymphocytes Simian immunodeficiency virus (SIV) Primate T lymphocytes Feline immunodeficiency virus (FIV) Cat T lymphocytes Bovine immune deficiency virus BIV) Cow Macrophages Equine infectious anemia virus (EIAV) Horse Macrophages Visna virus Sheep Macrophages The hypermutability of HIV, which mutates at a rate 1,000,000 times as great as that of eukaryotic DNA genomes, is important to the pathogenesis of HIV. The high error rate of HIV reverse transcriptase in vitro translates to approximately 5 to 10 errors per HIV genome per round of replication in vivo. This high error rate suggests that misincorporation by HIV reverse transcriptase is, at least in part, responsible for the hypermutability of the AIDS virus. Researchers hope that our understanding of the process may provide a basis for the systematic construction of antiviral nucleosides. In gene conversion, DNA segments are copied so that one sequence replaces sequences in another gene on the same chromosome. Studies of the sequences of different alleles have shown that the same sequences are found within several genes on the same chromosome, providing evidence for gene conversion. Gene duplication is the creation of an extra copy of a gene. This is a key mechanism in evolution. Once a gene is duplicated, the identical genes can undergo changes and diverge to create 2 different genes. Duplications typically arise from an event termed unequal crossing-over that occurs between misaligned homologous chromosomes during meiosis. Antigenic shift is the appearance of a new assortment of genes. This type of reassortment happens rarely and can be devastating, since shift produces a virus strain with a combination of surface antigen proteins to which the human population will have little or no immunity. Antigenic drift is caused by point mutations in the genes of microbes, such as the influenza virus. Every 2 to 3 years, a variant arises with mutations that allow the virus to evade neutralization by antibodies in the population. As new variants appear, they replace the previous variant so that within about 4 years, a given individual can be re-infected with an antigenic variant that has been gradually generated by infection of other individuals. This results in local epidemics.

Question 126

Human immunodeficiency virus, or HIV, is an enveloped human retrovirus of the lentivirus family. There is also a significant number of HIV-infected individuals who never become sick, never experience a decline in their CD4 counts, and never develop high plasma loads of viral RNA. The reasons that they never become sick include host factors such as the presence of mutations provide resistance to HIV, like mutations where? ## Footnote 1 CXCR4 2 CCR5 3 Mac-1 4 SDF-1 5 IL-8

Answer 126

CCR5 ## Footnote is a chemokine receptor that binds to several chemokines, as shown in the table. Refer to the table. Chemokine Produced by Receptor MIP-1α Monocytes, T cells, Mast cells, Fibroblasts CCR1,3,5 MIP-1β Monocytes, Macrophages, Neutrophils, Endothelium CCR1,3,5 RANTES T cells, Endothelium, Platelets CCR1,3,5 CCR5 is necessary for HIV entry into the host cell. CCR5 is expressed by macrophages, dendritic cells, and CD4 T cells. It is thought to be the major co-receptor for establishing primary infection, since individuals who are homozygous for a mutation in CCR5 appear to be resistant to infection by HIV. For example, the CCR5-Delta32 deletion mutation seems to confer resistance against HIV-1 by blocking its attachment to CCR5 so that HIV cannot gain entry to the cell. Development of drugs directed at chemokine receptors is thus an active area of research. CXCR4 is the other major co-receptor for HIV. Lymphotropic HIV uses CXCR4 found on T cells and requires a high density of CD4 on the cell surface. CXCR4 also binds the CXC-chemokine stromal-derived factor-1 (SDF-1) as a co-receptor. Both co-receptors are G-coupled proteins with 7 transmembrane spanning domains. Mac-1, also called CD11b/CD18, is stored in specific granules that are shuttled to the granulocyte surface. It exists as a chemoattractant activation-dependent molecule that undergoes a conformational change upon stimulation. Until stimulation occurs, it remains in a resting, non-adhesive state. Mac-1 is a β2 integrin. SDF-1 is a small chemokine of the CXC subfamily that is produced constitutively by bone marrow stromal cells and has an important role in early stages of B cell development. It is a growth factor for B cell progenitors and a chemotactic factor for T cells, monocytes, CD34+ hematopoietic progenitor cells, mature megakaryocytes, and dendritic cells. Interleukin-8 or IL-8, a CXC chemokine, is an 11-kDa homodimer of 99 amino acids that is also known as monocyte-derived neutrophil chemotactic factor (MDNCF). It is an important mediator of neutrophil, lymphocyte, and basophil chemotaxis and activation. It is released from several cell types in response to an inflammatory response.

Question 127

As part of your pathology rotation you are in the Electron Microscopy Lab of the University Hospital looking at EMs of cell cultures from a patient with a degenerative neurological illness. You observe what appear to be viral coats attached to the neural cell membranes. You conclude that the patient's illness is not likely to be caused by a retrovirus because ## Footnote 1 The retroviral life cycle begins when the virion lands on specific receptors and enters the cell, where the virion coat is removed in the cytosol 2 The retroviral life cycle begins when the virion lands on specific receptors and its contents enter the cell leaving the coat on the surface 3 The retroviral life cycle begins when the virion nonspecifically lands on the cell and enters the cell where the virion coat is removed in the cytosol 4 The retroviral life cycle begins when the virion lands on specific receptors and enters the cell, where the virion coat is removed in the mitochondrion 5 Retroviruses do not invade cells in culture

Answer 127

The retroviral life cycle begins when the virion lands on specific receptors and enters the cell, where the virion coat is removed in the cytosol ## Footnote Transposition occurs in eukaryotes in a fashion similar to that which occurs in prokaryotes. One type of transposition is quite similar to transposon insertion in bacteria. The other type of transposition occurs as in the first type, but it has a stage outside of the cell during which an infective element can be passed from one cell to the next. The first type has an element called a retroposon or a retrotransposon. This is a DNA copy of an RNA element, which inserts itself into the host genome. The retrotransposon has termini of short inverted repeats, and it generates short direct repeats of target DNA at the site of insertion. The role of these elements in the host cell is not clear. An example best explains the terms inverted repeats and direct repeats. If the retrotransposon has termini with the sequences 123 and 321, in that order from left to right, then this would be called inverted repeats. If the element recognizes the sequence in the host genome of AGTC, then upon insertion at this site, the termini would consist of AGTC123 and AGTC321 in that order from left to right. The AGTC sequence would be repeated but in the same direct order. The 123 would be repeated, but in inverted order. In the genome are footprints of ancient transposition events. It is interesting that direct target repeats flank certain sequences in the genome. These sequences suggest that they may have been RNA molecules at one time that have been converted into duplex DNA and inserted into the genome. The second type of transposition event involves an infective particle called a retrovirus. Retroviruses insert DNA copies of their RNA genomes into the host genome. The retrovirus recognizes and attaches to a cell-surface receptor on the host cell. The cell engulfs the particle and removes its coat, and then, the intracellular aspects of the life cycle of the virus begin. The cycle consists of an alternation between reverse transcription (RNA into DNA) and forward transcription (DNA into RNA). The RNA molecule brought into the cell by the infectious retrovirus is reversed transcribed into a DNA molecule that then integrates into the genome. The integrated DNA then forward transcribes an RNA molecule that either becomes packaged into another retrovirus, or it again becomes reversed transcribed into a DNA molecule that reinserts into the genome to repeat the cycle. The retroviral life cycle begins when the virion lands on specific receptors and enters the cell, where the virion coat is removed in the cytosol. The virus particle contains two copies of an RNA molecule. One of the copies is designated the (+) strand. In addition to the (+) strand, the virion also carries into the host cell the enzyme reverse transcriptase and a non-covalently attached tRNA molecule. The enzyme reverse transcriptase has three major activities: RNA-directed DNA synthesis, DNA-directed DNA synthesis, and RNA hydrolysis. The RNA molecule that the virion brings into the cell must be duplicated for the viral life cycle to continue. The steps of this process are as follows: Using the tRNA that the virion brings into the cell, the transcriptase engages in DNA synthesis in the 5' to 3' direction. This gives a short segment of DNA that is attached to the tRNA. This DNA is termed (-) DNA. RNAase activity of the transcriptase removes RNA bases paired with the newly formed DNA. The (+) RNA strand contains repeated sequences at each of its termini. The newly formed DNA-tRNA hybrid molecule pairs with the other end of the (+) RNA strand and the RNA is reversed transcribed into DNA. Most of the (+) RNA strand that is now paired with the newly synthesized DNA is hydrolyzed by the RNAase activity of the transcriptase. The remaining small segment of RNA is used as a primer to replicate a (+) DNA strand from the (-) DNA strand used as template. Any residual RNA is hydrolyzed. The newly formed (+) DNA strand pairs with the opposite end of the (-) DNA strand and primes the synthesis of the remaining (+) DNA strand. Each end of the (-) DNA strand consists of long terminal repeat sequences termed long terminal repeats (LTR).

Question 128

You wish to develop a retroviral inhibitor as part of your project at the Flumax Pharmaceutical Company. Of the many approaches that you might try, one that may have some success would be to target elements that are required for the life cycle of the viral particle. Some of these targets might be ## Footnote 1 Integrase and reverse transcriptase, which are carried in the virion 2 Integrase and reverse transcriptase, which are made by the host cell 3 Integrase and mutase, which are carried in the virion 4 Integrase and mutase, which are made by the host cell 5 Integrase and reverse transcriptase, which are carried by the covirion

Answer 128

Integrase and reverse transcriptase, which are carried in the virion ## Footnote Transposition occurs in eukaryotes in a fashion similar to that which occurs in prokaryotes. One type of transposition is quite similar to transposon insertion in bacteria. The other type of transposition occurs as in the first type, but it has a stage outside of the cell during which an infective element can be passed from one cell to the next. The first type has an element called a retroposon or a retrotransposon. This is a DNA copy of an RNA element, which inserts itself into the host genome. The retrotransposon has termini of short inverted repeats, and it generates short direct repeats of target DNA at the site of insertion. The role of these elements in the host cell is not clear. An example best explains the terms inverted repeats and direct repeats. If the retrotransposon has termini with the sequences 123 and 321, in that order from left to right, then this would be called inverted repeats. If the element recognizes the sequence in the host genome of AGTC, then upon insertion at this site, the termini would consist of AGTC123 and AGTC321 in that order from left to right. The AGTC sequence would be repeated but in the same direct order. The 123 would be repeated, but in inverted order. In the genome are footprints of ancient transposition events. It is interesting that direct target repeats flank certain sequences in the genome. These sequences suggest that they may have been RNA molecules at one time that have been converted into duplex DNA and inserted into the genome. The second type of transposition event involves an infective particle called a retrovirus. Retroviruses insert DNA copies of their RNA genomes into the host genome. The retrovirus recognizes and attaches to a cell-surface receptor on the host cell. The cell engulfs the particle and removes its coat, and then, the intracellular aspects of the life cycle of the virus begin. The cycle consists of an alternation between reverse transcription (RNA into DNA) and forward transcription (DNA into RNA). The RNA molecule brought into the cell by the infectious retrovirus is reversed transcribed into a DNA molecule that then integrates into the genome. The integrated DNA then forward transcribes an RNA molecule that either becomes packaged into another retrovirus, or it again becomes reversed transcribed into a DNA molecule that reinserts into the genome to repeat the cycle. The retroviral life cycle begins when the virion lands on specific receptors and enters the cell, where the virion coat is removed in the cytosol. The virus particle contains two copies of an RNA molecule. One of the copies is designated the (+) strand. In addition to the (+) strand, the virion also carries into the host cell the enzyme reverse transcriptase and a non-covalently attached tRNA molecule. The enzyme reverse transcriptase has three major activities: RNA-directed DNA synthesis, DNA-directed DNA synthesis, and RNA hydrolysis. The RNA molecule that the virion brings into the cell must be duplicated for the viral life cycle to continue. The steps of this process are as follows: Using the tRNA that the virion brings into the cell, the transcriptase engages in DNA synthesis in the 5' to 3' direction. This gives a short segment of DNA that is attached to the tRNA. This DNA is termed (-) DNA. RNAase activity of the transcriptase removes RNA bases paired with the newly formed DNA. The (+) RNA strand contains repeated sequences at each of its termini. The newly formed DNA-tRNA hybrid molecule pairs with the other end of the (+) RNA strand and the RNA is reversed transcribed into DNA. Most of the (+) RNA strand that is now paired with the newly synthesized DNA is hydrolyzed by the RNAase activity of the transcriptase. The remaining small segment of RNA is used as a primer to replicate a (+) DNA strand from the (-) DNA strand used as template. Any residual RNA is hydrolyzed. The newly formed (+) DNA strand pairs with the opposite end of the (-) DNA strand and primes the synthesis of the remaining (+) DNA strand. Each end of the (-) DNA strand consists of long terminal repeat sequences termed long terminal repeats (LTR). For it to function, the formed linear DNA must travel to the nucleus and be integrated into the host genome. The integration reaction is catalyzed by the viral product integrase, which is carried in the virion along with the reverse transcriptase. The integration of the viral DNA occurs at random sites in the host genome. Integrated proviral DNA is transcribed by the host enzymes to make viral RNAs. These RNA molecules can function both as mRNA and as inserts to make more virion particles.

Question 129

In some parts of the country cock-fighting or baiting is highly popular but illegal. You have been seeing a steady increase in the number of young to middle-aged males in your Neurology Practice who have a bizarre condition. It confers upon its victim's tics and tremors that produce movements similar to chickens scratching the ground with their feet. Hence, you name the syndrome: chicken scratch syndrome. You suspect that the patients have been around chickens and roosters infected with a retrovirus that attacks nerve tissues, but the patients deny being around chickens. You could bolster your theory as to the etiology of the syndrome if you could find antibodies in the serum of the patients that cross-reacted with: ## Footnote 1 The gag protein of retroviruses harvested from sick chickens 2 The mutase protein of retroviruses harvested from sick chickens 3 The isomerase protein of retroviruses harvested from sick chickens 4 The cytochrome oxidase protein of retroviruses harvested from sick chickens 5 The lactic dehydrogenase protein of retroviruses harvested from sick chickens

Answer 129

The gag protein of retroviruses harvested from sick chickens ## Footnote Transposition occurs in eukaryotes in a fashion similar to that which occurs in prokaryotes. One type of transposition is quite similar to transposon insertion in bacteria. The other type of transposition occurs as in the first type, but it has a stage outside of the cell during which an infective element can be passed from one cell to the next. The first type has an element called a retroposon or a retrotransposon. This is a DNA copy of an RNA element, which inserts itself into the host genome. The retrotransposon has termini of short inverted repeats and it generates short direct repeats of target DNA at the site of insertion. The role of these elements in the host cell is not clear. An example best explains the terms inverted repeats and direct repeats. If the retrotransposon has termini with the sequences 123 and 321, in that order from left to right, then this would be called inverted repeats. If the element recognizes the sequence in the host genome of AGTC, then upon insertion at this site the termini would consist of AGTC123 and AGTC321 in that order from left to right. The AGTC sequence would be repeated but in the same direct order. The 123 would be repeated, but in inverted order. In the genome are footprints of ancient transposition events. It is interesting that direct target repeats flank certain sequences in the genome. These sequences suggest that they may have been RNA molecules at one time that have been converted into duplex DNA and inserted into the genome. The second type of transposition event involves an infective particle called a retrovirus. Retroviruses insert DNA copies of their RNA genomes into the host genome. The retrovirus recognizes and attaches to a cell-surface receptor on the host cell. The cell engulfs the particle and removes its coat, and then the intracellular aspects of the life cycle of the virus begin. The cycle consists of an alternation between reverse transcription (RNA into DNA) and forward transcription (DNA into RNA). The RNA molecule brought into the cell by the infectious retrovirus is reverse-transcribed into a DNA molecule that then integrates into the genome. The integrated DNA then forward-transcribes an RNA molecule that either becomes packaged into another retrovirus or it again becomes reverse-transcribed into a DNA molecule that reinserts into the genome to repeat the cycle. The retroviral life cycle begins when the virion lands on specific receptors and enters the cell, where the virion coat is removed in the cytosol. The virus particle contains 2 copies of an RNA molecule. One of the copies is designated the (+) strand. In addition to the (+) strand, the virion also carries into the host cell the enzyme reverse transcriptase and a non-covalently attached tRNA molecule. The enzyme reverse transcriptase has 3 major activities: RNA-directed DNA synthesis, DNA-directed DNA synthesis, and RNA hydrolysis. The RNA molecule that the virion brings into the cell must be duplicated for the viral life cycle to continue. The steps of this process are as follows: Using the tRNA that the virion brings into the cell, the transcriptase engages in DNA synthesis in the 5' to 3' direction. This gives a short segment of DNA that is attached to the tRNA. This DNA is termed (-) DNA. RNAase activity of the transcriptase removes RNA bases paired with the newly formed DNA. The (+) RNA strand contains repeated sequences at each of its termini. The newly formed DNA-tRNA hybrid molecule pairs with the other end of the (+) RNA strand and the RNA is reverse-transcribed into DNA. Most of the (+) RNA strand that is now paired with the newly synthesized DNA is hydrolyzed by the RNAase activity of the transcriptase. The remaining small segment of RNA is used as a primer to replicate a (+) DNA strand from the (-) DNA strand used as template. Any residual RNA is hydrolyzed. The newly formed (+) DNA strand pairs with the opposite end of the (-) DNA strand and primes the synthesis of the remaining (+) DNA strand. Each end of the (-) DNA strand consists of long terminal repeat sequences termed long terminal repeats (LTR). For it to function, the formed linear DNA must travel to the nucleus and be integrated into the host genome. The integration reaction is catalyzed by the viral product integrase, which is carried in the virion along with the reverse transcriptase. The integration of the viral DNA occurs at random sites in the host genome. Integrated proviral DNA is transcribed by the host enzymes to make viral RNAs. These RNA molecules can function both as mRNA and as inserts to make more virion particles. The viral genome consists of a coding region that through different processing steps gives rise to different proteins. Translation from the first region until the first termination signal is encountered yields the gag product, which upon proteolysis yields components of the virion core. Suppression of the gag termination signal by a glutamyl-tRNA or by a ribosomal frameshift allows a single protein to be produced. This single protein then is further processed. The single protein consists of the gag protein and the pol protein. The pol protein generates reverse transcriptase, an endonuclease, and a protease. To produce the env protein, which is processed into different component of the virus envelope, the RNA molecule is spliced to produce a shorter subgenomic messenger coding for this protein. To produce an infective virion, the RNA and associated tRNA and enzymes are packaged into a core surrounded by capsid proteins; their extrusion takes place by the pinching off of a segment of host cell membrane, which then surrounds the core.

Question 130

Although the usual way in which a particle enters a cell is by phagocytosis so that the particle is enclosed in a phagocytic vacuole, there are other methods of entry. If viruses enter cells by phagocytosis, they are destroyed by hydrolytic enzymes. How do most nonenveloped and enveloped viruses enter cells? ## Footnote 1 Endocytosis 2 Opsonization 3 Neutralization 4 Phagocytosis 5 Pinocytosis

Answer 130

Endocytosis ## Footnote Most viruses enter the cell using endocytosis, the invagination of the plasma membrane into smaller virus-sized depressions coated on the cytoplasmic side with a cellular protein known as clathrin. These detach from the plasma membrane and become vesicles free in the cell's cytoplasm. These vesicles fuse with acidic compartments called endosomes. Endosomes then fuse with lysosomes containing degradative enzymes to reduce the ingested molecules to small breakdown products. Macrophages and other phagocytic cells have receptors for the Fc portion of the antibody molecule. These receptors provide a "handle" for phagocytes to bind coated particles. The coating of pathogens and foreign particles by antibodies is opsonization. The simplest and most direct way in which antibodies can protect from pathogens or their toxic products is by binding to them, thereby blocking their access to cells that they may infect or destroy. This is known as neutralization and is important for protection against bacterial toxins and against pathogens such as viruses, which can thus be prevented from entering cells and replicating. Phagocytosis is the ingestion of these coated pathogens or particles by macrophages or other phagocytes, followed by internalization and destruction by intracellular digestion. Pinocytosis is the simple cellular uptake of fluid and solutes. It is a much simpler process than phagocytosis.

Question 131

Epstein-Barr virus (EBV) was discovered during the search for a tumor-associated virus in African Burkitt's lymphoma. The link between EBV and Burkitt's lymphoma was substantiated by the detection of the EBV genome and EBV-associated antigens in tumor cells. The genetic rearrangements that result from EBV infection are believed to activate oncogenes and result in malignancy. EBV is unique among human viruses in that it produces disease by transforming what? ## Footnote 1 Neutrophils 2 Lymphocytes 3 Eosinophils 4 Basophils 5 Mast cells

Answer 131

Lymphocytes ## Footnote EBV, or human herpesvirus 4, transforms B-lymphocytes, which are then self-perpetuating; they multiply like tumor cells, and small numbers may produce free virus that can transform other B-lymphocytes. Up to half of the lymphoid cells from the tonsils of EBV-infected patients may be EBV-transformed. Primary EBV infection is stopped by 2 defenses: a suppressor and cytotoxic T cell immune response capable of eliminating almost all virus-infected cells, and virus-neutralizing antibodies that prevent the spread of infection from one target cell to another. The characteristic "atypical lymphocytes" are predominantly CD8+ cytotoxic T lymphocytes that recognize and destroy EBV-infected B cells. Neutrophils are phagocytic cells that are an important component of the innate immune response. They have functions similar to macrophages but remain in the bloodstream until recruited to sites of infection. Eosinophils are thought to be important chiefly in defense against parasitic infections. They are terminally differentiated, end-stage leukocytes that reside primarily in submucosal tissue and are recruited to sites of specific immune responses. They are granulocytes that can express Fc receptors when activated. Once these receptors are triggered they degranulate, releasing leukotrienes that cause muscle contraction. Basophils are the smallest circulating granulocytes with the least known function. Their function is probably similar and complementary to that of eosinophils and mast cells. They arise in the bone marrow, and following maturation and differentiation, are released into the blood circulation. Like mast cells, basophils have receptors on their cell membranes that bind with high affinity to the Fc portion of IgE. Mast cells reside mainly near small blood vessels. They are large cells containing distinctive cytoplasmic granules that contain a mixture of chemical mediators, including histamine, that act rapidly to make local blood vessels more permeable. Mast cells are believed to play a part in protecting mucosal surfaces against pathogens.

Question 132

A 7-year-old boy who lives in Uganda develops a large, disfiguring mass on his jaw. The mass develops rapidly. A biopsy confirms that he has lymphoma. The pathologist comments that on histologic examination, the biopsy looks like a "starry sky". What virus is associated with the development of this type of lymphoma? ## Footnote 1 Human papilloma virus 2 Hepatitis B 3 Varicella-zoster virus 4 HTLV-1 5 Epstein-Barr virus

Answer 132

Epstein-Barr virus ## Footnote This boy has Burkitt's lymphoma. Burkitt's lymphoma is neoplasm of B cells. Burkitt's lymphoma can be either endemic (the African form of Burkitt's' lymphoma) or non-endemic. A large percentage of the cases of African Burkitt's lymphoma involve the jaw. The phrase "starry sky" is a descriptive phrase for the pathologic appearance on microscopy. Epstein Barr virus is a herpesvirus. Epstein Barr virus is the cause of infectious mononucleosis. Epstein-Barr virus is associated with the development of the African form of Burkitt's lymphoma. Epstein-Barr virus is also associated with nasopharyngeal carcinoma. Hepatitis B virus is a DNA virus. It is also referred to as the Dane particle. There is an association of hepatitis B infection and the development of hepatocellular carcinoma. Human papilloma virus is a papovavirus. Human papilloma virus is responsible for warts. Human papilloma virus is associated with the development of cervical cancer. Varicella-zoster virus is a herpesvirus. Varicella zoster virus is responsible for chicken pox and shingles, among other things. Varicella-zoster virus is not associated with the development of cancer in men. HTLV is a retrovirus. HTLV-I is associated with T-cell leukemia/lymphoma.

Question 133

A nosocomial outbreak of a viral respiratory illness occurs in a pediatric ward during winter season. The causative viral agent is a recognized major respiratory pathogen of young children and infants. It is a paramyxovirus that does not have haemagglutination and neuraminidase activities. What is a feature of infection by this virus? ## Footnote 1 Transmission can occur through contaminated fomites 2 Infants having maternal antibodies are immune to the infection 3 In adults, the infection is always asymptomatic 4 Responds to the antiviral agent Oseltamivir 5 Immunoprophylaxis is the method of choice to control nosocomial spread

Answer 133

Transmission can occur through contaminated fomites ## Footnote Transmission of RSV occurs through respiratory secretions by direct contact with the infected person or through contaminated fomites. Paramyxoviruses of human importance are Parainfluenza viruses, Respiratory syncytial virus (RSV), Mumps, Measles (rubeola), and Newcastle disease viruses. Of these RSV is the only virus that lacks in haemagglutinating and neuraminidase activities. RSV is the major respiratory pathogen of young children and the foremost cause of lower respiratory tract infections in the form of bronchiolitis and pneumonia in infants. Epidemics are frequent in late fall and winter. RSV is an important nosocomial pathogen. It can be concluded that RSV is responsible for the nosocomial outbreak in the pediatric ward. Transmission of RSV occurs through respiratory secretions by direct contact with the infected person or through contaminated fomites. Inhalation of aerosols produced by coughing and sneezing can cause infection. Touching the contaminated fomites results in contamination of fingers. Accidental self-inoculation of nares or conjunctiva by contaminated finger leads to infection. Nosocomial transmission often occurs via health care personnnel. Contact isolation precautions are necessary to manage RSV nosocomial outbreaks. These include isolation of infected patients, restriction of visitors, and strict adherence of medical personnel to contact precautions such as hand washing, wearing gowns and gloves, masks, and eye protection. RSV infection does not show the other features listed. Maternal antibodies are not found to be protective. Rates of illness are highest among 1 to 6-month-old infants and severe illness has been observed in infants with moderate level of maternal antibodies. Nasal IgA neutralizing antibodies are thought to have more protective effect than serum antibodies. Cell mediated immunity is thought to play an important role in protection against RSV infection. Re-infections are common, and infected older children and adults get common cold-like symptoms. Severe lower respiratory tract disease can occur in elderly and immunocompromised persons. Immunoprophylaxis is not used for controlling spread during outbreaks in health-care settings as in pediatric wards. Immunoprophylaxis (RSV immunoglobulin or monoclonal antibodies) is used to protect children at risk, such as prematurely born infants and children <2 years old with bronchopulmonary dysplasia. Oseltamivir is a neuraminidase inhibitor; it is not effective against RSV. Ribavirin aerosol is used for treatment of bronchiolitis and pneumonia due to RSV infection.

Question 134

Case A group of teens goes on an exploration trip. Against the advice of her friends, a 15-year-old girl goes off by herself and enters a cave. She sees a bat that is unable to fly and, in an attempt to see if it is hurt, approaches it. Unfortunately, she gets bitten by the bat. Because she had been forewarned about entering the cave, she is too embarrassed to tell anybody about the bite. Besides which, the bite marks are small, so she is not concerned. A few weeks after the trip, she becomes very ill. She develops fever, headache, and fatigue. This is followed by hallucinations, seizures, and episodes of agitation. In addition, when she swallows, she has dramatic muscle spasms. She progresses to a coma and then dies. What would be found on autopsy in her brain? ## Footnote 1 Döhle bodies 2 Russell bodies 3 Foam cells 4 Howell-Jolly bodies 5 Negri bodies

Answer 134

Negri bodies ## Footnote The girl contracted rabies from the bat bite. Since she did not tell anybody about the incident, appropriate prophylactic measures were not taken. The neurologic symptoms she had are all consistent with rabies infections. Rabies is also referred to as hydrophobia because of the muscle spasms that occur when swallowing. The virus which causes rabies is a member of the family of Rhabdoviridae (rhabdovirus). The virus contains a single strand of RNA. Negri bodies are cytoplasmic inclusions seen with rabies. Döhle bodies are seen in white blood cells with burns, infections, trauma, and some other conditions. Russell bodies are intracellular accumulations of protein. Foam cells are lipid-laden macrophages. Howell-Jolly bodies are nuclear remnants seen in red blood cells, particularly after splenectomy.

Question 135

A 32-year-old new male patient presents for a routine physical exam. The patient confides that he is HIV positive; he has not sought any medical help. During examination of his oral cavity, raised areas that are whitish-tan in color with feathery appearance on his tongue are noted. Attempts to scrape the area off for sampling are unsuccessful. What is the most likely diagnosis? ## Footnote 1 Hairy leukoplakia 2 Atrophic glossitis 3 Hairy tongue 4 Geographic tongue 5 Candidiasis

Answer 135

Hairy leukoplakia ## Footnote Hairy leukoplakia may be seen in people infected with HIV and AIDS. It is characterized by raised areas that are whitish-tan in color and have a feathery appearance. It is different from candidiasis of the tongue in that hairy leukoplakia cannot be scraped off. A "hairy tongue" is not actually due to hair growth on the tongue; it consists of elongated papillae that have the appearance of grayish-black hair to the naked eye. This condition may be caused by antibiotic use, or there may not be any reason. Atrophic glossitis (or smooth tongue) presents as having a smooth surface due to papillae loss. The loss may indicate deficiency in riboflavin, niacin, folic acid, vitamin B12, pyridoxine, or iron. A geographic tongue is a benign condition with an unknown cause; it is characterized by a map-like pattern of smooth red areas that do not have papillae as well as rough areas that still have papillae. Although candidiasis is also common with people with AIDS and the infection also causes the tongue to have a white coating; the coat can be scraped and a sample can be analyzed for the presence of Candida.

Question 136

Case A 19-year-old female college student starts to feel weak and tired. She becomes ill with a fever, accompanied by a sore throat. After 1 week, she is seen by student health services. Upon further questioning, she denies a runny nose or nasal congestion. She denies sputum production or cough. On physical examination, she is noted to be febrile; there is cervical lymphadenopathy. Her oral cavity and pharynx are slightly edematous. Her spleen is palpable. Blood is drawn, and her laboratory results are as follows: TEST RESULTS REFERENCE RANGE Hematocrit 42 40-50 (male) 36-44 (female) Hemoglobin 14 gm/dL 13.8-17.2 gm/dL (male) 12.1-15.1 gm/dL (female) RBC 4.8 x 106/µl 4.5-5.7 x 106/µl (male) 3.9-5.0 x 106/µl (female) Platelets 250,000/mm3 130,000-400,000/mm3 Mean corpuscular volume 92 cu µ 80-100 cu µ WBC 15.4 x 103/mm3 4.0-11 x 103/mm3 Neutrophils 41 40-75% Lymphocytes 56 15-45% Monocytes 2 1-10% Eosinophils 1 1-6% Basophils 0 0-2% Comments: Numerous atypical lymphocytes are seen. What is the cause of her disease? ## Footnote 1 Epstein-Barr virus 2 Candida albicans 3 Respiratory syncytial virus 4 Rhinovirus 5 Coxsackievirus

Answer 136

Epstein-Barr virus ## Footnote This patient has signs and symptoms of infectious mononucleosis, which include fever, sore throat, splenomegaly, and lymphadenopathy. She has a lymphocytosis with atypical lymphocytes, which is also characteristic. The atypical lymphocytes are T cells. Epstein-Barr virus is the cause of infectious mononucleosis. The B cells are infected by the Epstein-Barr virus. Candida albicans is the etiologic agent in thrush. Thrush is oral candidiasis, and there would be white patches visible on oral examination. Respiratory syncytial virus is a pathogen commonly seen in very young children. It causes a respiratory illness that is characterized by rhinorrhea, fever, and cough. Although she has a fever, this patient denies rhinorrhea and cough. In addition, she is not within the normal age range for infection by a respiratory syncytial virus. Rhinovirus is the cause of colds. There would not be a lymphocytosis with atypical lymphocytes with the common cold. There would also not be splenomegaly or lymphadenopathy. In addition, the symptoms would include rhinorrhea (runny nose) and nasal congestion. Coxsackievirus is the cause of hand-foot-mouth disease. With hand-foot-mouth disease, one would expect to see vesicles or ulcers in the patient's mouth and pharynx. In addition, her hands and feet would be involved.

Question 137

Case A 19-year-old female college student starts to feel weak and tired. She becomes ill with a fever, accompanied by a sore throat. After a week, she is seen by student health services. Upon further questioning, she denies runny nose and nasal congestion. She denies sputum production and cough. On physical examination, she is noted to be febrile and she has cervical lymphadenopathy. Her oral cavity and pharynx are slightly edematous. Her spleen is palpable. Blood is drawn, and her laboratory results are as follows: TEST RESULTS REFERENCE RANGE Hematocrit 42 40-50 (male) 36-44 (female) Hemoglobin 14 gm/dL 13.8-17.2 gm/dL (male) 12.1-15.1 gm/dL (female) RBC 4.8 x 106/µl 4.5-5.7 x 106/µl (male) 3.9-5.0 x 106/µl (female) Platelets 250,000/mm3 130,000 - 400,000/mm3 Mean corpuscular volume 92 cu µ 80-100 cu µ WBC 15.4 x 103/mm3 4.0-11 x 103/mm3 Neutrophils 41 40 -75% Lymphocytes 56 15-45% Monocytes 2 1-10% Eosinophils 1 1-6% Basophils 0 0-2% Comments: Numerous atypical lymphocytes are seen. What cell is infected? ## Footnote 1 B cells 2 T cells 3 Monocytes 4 Neutrophils 5 Basophils

Answer 137

B cells ## Footnote This patient has signs and symptoms of infectious mononucleosis. Fever, sore throat, fatigue, malaise, anorexia, and myalgia typically occur in the early phase of the disease. Physical findings include lymphadenopathy and splenomegaly. Infectious mononucleosis is associated with granulocytopenia followed within 1 week by a lymphocytic leukocytosis with atypical lymphocytes. The B cells are infected by the Epstein-Barr virus; T cells, monocytes, neutrophils, and basophils are not.

Question 138

Case A 23-year-old sexually active graduate student develops painful sores on his penis. He ignores them for a while and they go away. Several months later, shortly before his final exams, they recur. This time, he goes to the student health services office. On physical examination, he has a fever and tender, enlarged inguinal lymph nodes. There are numerous vesicular sores on a red tissue. What is the most likely diagnosis? ## Footnote 1 Primary syphilis 2 Condyloma acuminatum 3 Herpes genitalis 4 Chancroid 5 Gonorrhea

Answer 138

Herpes genitalis ## Footnote This man has signs and symptoms of herpes genitalis. The lesions caused by herpes genitalis are vesicular lesions on an erythematous foundation. Soft, painful adenopathy can be seen with herpes genitalis as well as fever. In primary syphilis, there is a painless chancre along with painless regional lymphadenopathy. Darkfield examination of a lesion will show the spirochetes in the majority of cases. Lesions do not typically wax and wane. Condyloma acuminatum is the cause of genital warts. These are caused by human papilloma virus. Lesions do not typically appear and reappear. The ulcer seen with chancroid would be painful. There would be painful tender nodes with chancroid. The lesions described are not chancroid. Gonorrhea can present with symptoms of urethritis. A purulent discharge and dysuria are consistent with gonorrhea. Intracellular diplococci on a Gram stain of the urethral discharge is also consistent with the diagnosis of gonorrhea.

Question 139

Case A 25-year-old woman who is 36 weeks pregnant presents for her regular obstetrics care examination. She was diagnosed with hepatitis C a couple years ago. No viral RNA was detected during her pregnancy, which progressed smoothly and without major discomfort. She has no history of intravenous drug use or blood transfusions. She is HIV negative. She plans on breastfeeding, but she is concerned about transmitting the hepatitis C virus to the newborn. How do you advise this patient regarding breastfeeding her infant? ## Footnote 1 Breastfeed; the virus will be transmitted during birth. 2 Breastfeed; there is no risk to the newborn. 3 Breastfeed, but temporarily stop if nipples crack or bleed. 4 Breastfeed, but maintain good hygiene of the nipples. 5 Breastfeed, but undergo treatment with pegylated IFNα.

Answer 139

Breastfeed, but temporarily stop if nipples crack or bleed. ## Footnote Transmission of the HCV through breast milk has not been observed, but cracked and bloody nipples could facilitate the infection of the baby, as hepatitis C is a bloodborne illness. A small viral load—below detection level—could potentially infect the baby. Even though hepatitis C is a bloodborne disease that can be transmitted from an infected mother to her newborn, when no viral RNA is detected in the mother, the neonate is not infected. This patient has no history of intravenous drug use or HIV. The risk of viral infection for her baby is low. Even though it is generally correct that mother's milk does not contain HCV, contact with bloody nipples might facilitate viral transmission while breastfeeding. Maintaining good nipple hygiene does not remove the risk of viral transmission from cracked or bloody nipples or areolas. Pegylated interferon-alpha (IFNa) is an IFNa molecule that has been covalently linked to polyethylene glycol for better absorption and longer half-life, commonly used for treatment of chronic hepatitis C in adults. Treatment with interferon leads to a temporary reduction in white blood cells and platelets and increased vulnerability to infection, bleeding, or bruising. Because the degree of IFN transmission to babies through human milk is unknown, it is advisable not to breastfeed while being treated with IFN.

Question 140

Case A 27-year-old pregnant woman who recently returned from a medical mission in Uganda develops anorexia, followed by jaundice, abdominal pain, and an acute severe increase in liver enzymes. She has no other medical problems and does not use illicit drugs, tobacco, or alcohol. Laboratory diagnosis reveals a (+) RNA virus. HAV-IgG and HAV-IgM are negative. HBsAg and HBcAb are negative, but HBsAb is positive. What is the most probable cause of this infection? ## Footnote 1 Hepatitis A 2 Hepatitis B 3 Hepatitis C 4 Hepatitis D 5 Hepatitis E

Answer 140

Hepatitis E ## Footnote The correct answer is Hepatitis E. Hepatitis E is a single-stranded (ss) RNA virus that is transmitted by the fecal-oral route. In developing countries, it is a cause of epidemics of acute hepatitis, often as a result of contaminated water. There is no chronic or carrier state associated with Hepatitis E infection, and the infection is very mild in some patients; however, pregnant women are especially at risk of developing severe acute liver failure that is sometimes fatal. Hepatitis A is also a ssRNA virus that produces gastrointestinal illness, often through ingestion of contaminated food or water. The fact that the IgM and IgG antibodies are negative in this patient indicates that he has not been exposed to this virus. Hepatitis B is the only hepatitis virus that is a DNA rather than an RNA virus. It is a bloodborne pathogen that may cause acute hepatitis, marked by elevated liver enzymes. Chronic liver disease due to carriage of the virus is also common. This patient has HBs antibody but no HBs antigen and no HBc antibody. This is the classic profile of someone who has been vaccinated against Hep B infection. Hepatitis C is also a bloodborne virus that causes chronic liver disease. At the time of acute infection, many patients have no symptoms. Flu-like symptoms appear in some patients, but not typically gastrointestinal complaints. Hepatitis D is a bloodborne virus that occurs as a co-infection in some patients with Hepatitis B. In these patients, fulminant hepatitis is more likely to occur.

Question 141

Case A 3-year-old girl develops diarrhea, vomiting, and abdominal cramps. Examination of a stool sample reveals an icosahedral-shaped DNA virus with long penton fibers protruding from the virus. What is the most likely cause of the child’s illness? ## Footnote 1 Adenovirus 2 Rotavirus 3 Parvovirus B19 4 Coronavirus 5 Norovirus

Answer 141

Adenovirus ## Footnote The symptoms and description of the virus are most consistent with adenovirus infection. The adenovirus is a DNA virus that replicates in the nucleus. Its structure is unique in that it has an icosahedral shape and characteristic fibers projecting from its surface. Rotavirus causes gastroenteritis in children; however, it is an RNA virus, not a DNA virus. Rotavirus vaccine has now greatly reduced the occurrence of this infection. Parvovirus B19 is also an icosahedral DNA virus; however, it produces erythema infectiosum ("slapped cheek" syndrome), not gastroenteritis. It may also cause aplastic anemia, especially in patients with sickle cell disease. Coronavirus is a helical single-stranded RNA virus. It causes upper respiratory illnesses, not gastroenteritis. Norovirus is an icosahedral virus that causes gastroenteritis; however, it is an RNA, not a DNA, virus.

Question 142

Case Highlights A group of teens goes on an exploration trip. Against the advice of her friends, a 15-year-old girl goes off by herself and enters a cave. A few weeks after the trip, she becomes very ill. She develops fever, headache, and fatigue. This is followed by hallucinations, seizures, and episodes of agitation. In addition, when she swallows, she has dramatic muscle spasms. She progresses to a coma and then dies. Autopsy reveals the presence of Negri bodies in the brain. What was the condition that led to the patient's death? ## Footnote 1 Colorado tick fever 2 Rabies 3 West Nile virus 4 Eastern equine encephalitis 5 St. Louis encephalitis

Answer 142

Rabies ## Footnote The girl most likely contracted rabies from the bite of a bat present in the cave that she entered. A characteristic pathological finding in rabies is the presence of Negri bodies in the central nervous system. Negri bodies are cytoplasmic inclusion bodies that are visible upon staining of CNS tissue with hematoxylin and eosin. Colorado tick fever is a febrile illness transmitted by a tick. Negri bodies are not characteristic of this infection. West Nile virus, Eastern equine encephalitis, and St. Louis encephalitis produce encephalitis and are all transmitted by mosquitos. Negri bodies are not characteristic of these infections.