Ch 6, 25, 26 Flashcards

Question

Process of synthesis

Answer 1

Using to make viral proteins and nucleic acids A. Copy Genome B. Make viral proteins - varies depending on whether the virus is a DNA or RNA virus - DNA viruses generally are replicated and assembled in the nucleus - often use host enzymes - RNA viruses generally are replicated and assembled in the cytoplasm - often use viral enzymes; RdRp = RNA-dependent RNA polymerase - must make or bring with it - positive-sense RNA contain the message for translation - negative-sense RNA must be converted into positive-sense message

Answer 2

Various consequences to host cell; chronic release (budding or exocytosis) Or lysis/cell death

Answer 3

- cell harbors the virus and is not immediately lysed - can last weeks or host’s lifetime; several can periodically reactivate - chronic latent state - some animal viruses enter the host cell and permanently alter its genetic material, resulting in cancer - these viruses are termed oncogenic, and their effect on the cell is called transformation - transformed cells have an increased rate of growth, alterations in chromosomes, and the capacity to divide for indefinite time periods resulting in tumors - mammalian viruses capable of initiating tumors are called oncoviruses - papilloma virus - cervical cancer - Epstein-Barr virus - Burkitt’s lymphoma

Answer 4

Cytopathic effects: cell damage altering microscopic appearance - disorientation of individual cells - gross changes in shape or size - intracellular changes (inclusion bodies, syncytium)

Answer 5

- smallpox:cells round up; inclusions appear in cytoplasm - herpes simplex: cells fuse to form multi nucleated syncytia; nuclear inclusions - adenovirus: clumping of cells; nuclear inclusions - poliovirus: cell lysis; no inclusions - renovirus: cell enlargement; vacuoles and inclusions in cytoplasm - influenza virus: cells round up; no inclusions - rabies virus: no change in cell shape; cytoplasmic inclusions (Negri bodies) - measles virus: syncytia form (multinucleate)

Answer 6

- viruses are the most common cause of acute infections - several billion viral infections per year - some viruses have high mortality rates - possible connection of viruses to chronic afflictions of unknown cause - viruses are major participants in the earth’s ecosystem

Answer 7

- more difficult than other agents - consider overall clinical picture - take appropriate sample - infect cell culture - look for characteristic Cytopathic effects - screen for parts of the virus - screen for immune response to virus (antibodies) - antiviral drugs can cause serious side effects

Answer 8

- viruses are very different from other infectious agents - to truly understand them, you need a very firm grasp on the basics of DNA structure and replication, RNA transcription, and protein translation process - the trick with each type is to ask what is the shortest set of cellular events to get from the viral genome inserted into the cell to newly-made virus particles - events for each group of viruses will come in handy when thinking about how to interrupt these cycles with antiviral drugs

Answer 9

- non-enveloped, ssDNA - primarily transmitted via direct/indirect contact - small diameter and genome size - causes distemper in cats, enteric disease in dogs, fatal cardiac infection in puppies - few cause infections in humans B19 cause of erythema infectiosum (fifth disease); rash of childhood - children may have fever and rash on cheeks (-slap-face-rash) - severe fatal anemia can result if pregnant woman transmits virus to fetus (low but know risk)

Answer 10

Papilloma: squamous epithelial growth, wart, or verruca - cause by 100 different strains of HPV - transmissible through direct contact or contaminated fomites; incubation - 2 weeks to more than a year - most common warts regress over time; they can be removed by direct chemical application of podophyllin and physical removal by cauterization, freezing, or laser surgery - warts can recur - warts described by location - common seed warts: painless, elevated rough growth; on fingers, etc - plantar warts: deep, painful; on soles of feet - genital warts: most common STD in US, morphology ranges from tiny, flat, inconspicuous bumps to extensive, branching, cauliflower-like masses - warts are good at causing uncontrolled growth of cells and avoiding immune recognition - ten HPV types increase risk for developing reproductive cancer; 2 (HPV16 and HPV 18) account for 70% for metastatic tumors - early detection through inspection of genitals, women Pap smear to screen for abnormal cervical cells - three effective HPV vaccines have been approved by the FDA: Ceravix, Gardasil, and Gardasil 9)

Answer 11

- non enveloped, dsDNA 30 types associated with human disease (oncogenic only in animals) - infect lymphoid tissue, respiratory and intestinal epithelia and conjunctiva - spread by respiratory and ocular secretions - causes colds, pharyngitis, conjunctivitis, keratoconjunctivitis, acute hemorrhagic cystitis Severe cases with interferon.

Answer 12

Produce eruptive skin pustules (pocks or pox) that leaves scars - largest and most complex animal viruses - have the largest genome of all viruses - dsDNA - multiply in cytoplasm in factory areas (break the normal “rules”) - specificity for cytoplasm of epidermal cells and subcutaneous connective tissues

Answer 13

First (and ONLY) disease to be eliminated by vaccination - maybe Guinea Worm Disease - others are painfully close (polio, measles, mumps, rubella, tape worm, filariasis) - exposure through inhalation or skin contact - infection associated with fever, malaise, prostration, and a rash - Variola major: highly virulent, caused toxemia, shock, and intravascular coagulation - Variola minor: less virulent

Answer 14

1. Vaccine - effect prophylactically and therapeutically 2. Human only host 3. Clear mechanism of transmission - isolation to prevent spread 4. Obvious signs of disease

Answer 15

- the smallpox vaccine uses a single drop of vaccina virus punctured into the skin with a double pronged needle - routine vaccination ended in 2002 for military and medical personnel - reintroduced to address mpox outbreak in 2022

Answer 16

MPOX is typically associated with small animals (guinea pigs, not just simians) - two common clades associated with human infections (West African/Congo Basin) - 2022 outbreak associated with the less severe West African clade - not considered an STI however in 2022 primarily associated MSM

Answer 17

Molluscipoxvirus: much more common Poxviruses. It causes a skin disease called molluscum contagious (think waxy warts) - distributed throughout the world, with highest incidence occurring in certain Pacific Islands - in endemic areas, it is primarily an infection of children - transmittted by direct contact and fomites - in US, most commonly an STD - lesions are small, smooth macules in genital area and thighs - AIDS patients suffer an atypical form which attacks the skin of the face and forms tumor-like growth Treatment: freezing, electrical cautery, chemical agents (similar to warts) - many mammalian groups host some poxvirus - cowpox, rabbit pox, mouse pox, elephant pox - monkeypox in humans - skin pocks, fever, swollen lymph nodes - cowpox in humans - rare, usually confined to hands; cutaneous sites can be involved

Answer 18

- all members show latency and cause recurrent infection; viral DNA forms episome - clinical complications of latency and recurrent infections become more severe with advancing age, cancer chemotherapy, or other conditions that compromise the immune defenses - common and serious opportunists among AIDS patients - large enveloped Icosahedral dsDNA - replicates within nucleus - most successful virus in humans

Answer 19

- HHV1 & HHV2: (HSV - herpes simplex virus 1 & 2) - fever, blisters, and genital infections - HHV3: (VZV - varicella-zoster virus) - chickenpox and shingles - HHV4: ( EBV - Epstein-Barr Virus) - associated with infection of the lymphoid tissue - HHV5: (CMV - cytomegalovirus) - infects the salivary glands and other visceral - HHV6/7: (HHV) - roselola - HHV8: (KSHV) - implicated in kaposi sarcoma

Answer 20

Human are susceptible to 2 varieties: - HSV1: usually lesions on the oropharynx, cold sores, fever blisters - occurs early in childhood - HSV2: lesions on genitalia, possibly oral - occurs in ages 14-29 - can be spread without visible lesions Transmission by direct exposure to secretions consigning the virus; active lesions most significant source; genital herpes can be changed transmitted in the absence of lesions - HSV multiplies in sensory neurons, moves to ganglia - HSV1 enters 5th cranial nerve - HSV2 enters lumbosacral spinal nerve trunk ganglia Recurrent infection is triggered by various stimuli - fever, UV radiation, stress, mechanical injury Newly formed viruses migrate to body surfaces, producing a local skin or membrane lesion

Answer 21

- Herpes labialis: (fever blisters or cold sores) - most common recurrent HSV-1 infection - herpetic gingivostomatitis especially in young children - inflammation of the oral mucosa (gums, tounge, soft palate, and lips) - Herpetic Keratitis: (ocular herpes) - inflammation of the eye, latent virus travels into the ophthalmic rather than the mandibular branch of trigeminal nerve - gritty feeling in the eye, conjunctivitis, sharp pain, and sensitivity to light

Answer 22

- genital herpes: starts with malaise, anorexia, fever, bilateral swelling and tenderness in the groin; clusters of sensitive vesicles on the genitalia, perineum, and buttocks; urethritis, painful urination, cervicitis, itching; vesicles ulcerate - recurrent bouts usually less severe, triggered by menstruation, stress, and concurrent bacterial infection

Answer 23

HSV-1 and HSV-2 infections are potentially fatal in the neonate and fetus - infant contaminated by mother before or during birth; hand transmission by mother to infant - infection of mouth, skin, eyes, CNS Preventative screening of pregnant women; delivery by c-section if outbreak at the time of birth

Answer 24

Herpetic whitlow: HSV-1&2 can penetrate a break in the skin and cause a localized infection, usually on one finger; extremely itchy and painful - workers in the fields of obstetrics, gynecology, dentistry, and respiratory therapy at greatest risk HSV-1 encephalitis: rare complication but most common sporadic form of viral encephalitis in the US, life threatening - those with underlying immunodeficiency are prone to severe disseminated herpes

Answer 25

- Diagnosis: vesicles and exudate are typical diagnostic symptoms, scrapings from base of lesions showing giant cells, culture and specific tests for diagnosing severe or disseminated HSV; direct fluorescent antibody tests - Treatment: acyclovir, famiciclovir, valacyclovir; topical medications - one of the few viral diseases we have therapeutic options for

Answer 26

Humans only natural host. Infection transmitted by respiratory droplets and contact - primary infection: varicella (chickenpox) - characteristic vesicles - virus enters neurons and remains latent - reaction of the viruses - Herpes zoster (shingles) - dermatomes. More common in older patients - activated in ganglion by stress - viruses migrate down sensory nerve to skin *multiple dermatome or bilateral lesions = immune suppression

Answer 27

Diagnosis: cutaneous manifestations of varicella and shingles are sufficiently characteristic for ready clinical recognition - shingles can be confirmed from multinucleate giant cells in stained smears prepared from vesicle scrapings - unequivocal shingles identification with florescent antibody detection of viral antigen in skin lesions, dna typing, or culture Treatment: treat symptoms in uncomplicated infections; acyclovir, famciclovir, interferon for systemic disease - live attenuated vaccine (varivax) for chickenpox and shingles

Answer 28

Think B cells! Ubiquitous virus: infects lymphoid tissue and salivary glands Transmission - direct, oral contact and contamination with saliva - in industrialized countries, college-age population is vulnerable to infectious mononucleosis (mono - kissing disease) - by mid-life, 90-95% of all people are infected - anyone with an immune deficiency is highly susceptible Infectious mononucleosis - sore throat, high fever, cervical lymphadenopathy; develop after 30-50 day incubation Dormancy in B cells; reactivated may be asymptomatic

Answer 29

Burkitt Lymphoma: B cell malignancy - usually develops in jaw and grossly swells the cheek - affects Central African children 4-8 years old - may be associated with chronic coinfections with malaria Nasopharyngeal carcinoma: malignancy of epithelial cells - affects older Chinese and African

Answer 30

Diagnosis - differential blood count shows lymphocytosis, neutropenia, and large atypical lymphocytes - serological assays to detect antibodies and antigen Treatment: directed at relief of symptoms of fever and sore throat - disseminated disease may be treated with IV gamma, globulin, interferon, acyclovir, and monoclonal antibodies

Answer 31

Produce giant cells with nuclear and cytoplasmic inclusions Transmitted in saliva, respiratory mucus, milk, urine, semen, cervical secretions - commonly latent in various tissues - most infections are asymptomatic - 3 groups develop a more virulent form of disease: fetuses, newborns, immunodeficient adults Newborns may exhibit enlarged liver and spleen, jaundice, capillary bleeding, microcephaly, and ocular inflammation; may be fatal - babies who survive develop neurological sequelae, hearing, visual disturbances and mental retardation Perinatal CMV infection - mostly asymptomatic, or pneumonitis, and a mononucleosis-like syndrome Transplant patients - pneumonitis, hepatitis, myocarditis, meningoencephalitis (David Vetter) AIDS patients - CMV mononucleosis, disseminated CMV, retinitis

Answer 32

Human B-lymphotrophic virus - transmitted by close contact with saliva and other secretions; very common - causes rosella, an acute febrile disease in babies 2-12 months; begins with fever, followed by a faint maculopapular rash; usually self-limited - adults may get mono-like symptoms, lymphadenopathy and hepatitis - over 70% of MS patients show signs of infection - clinical studies have shown significant relationship between HHV-6 and Hodgekin’s lymphoma, oral carcinoma, certain T cell leukemias - HHV-7 is closely related to HHV-6 and causes similar diseases

Answer 33

Kaposi’s sarcoma-associated virus (KSHV) or HHV-8 is linked with common tumor of AIDS patients; also may be involved in multiple myeloma

Answer 34

- enveloped DNA viruses - never been grown in tissue culture - unusual genome containing both double and single stranded DNA (weird - own Baltimore classification) - tropism for liver

Answer 35

Multiplies exclusively in the liver, which continuously seeds blood with viruses - chronic - 10^7 virions/mL blood - minute amounts of blood, blood products can transmit infection; sexually transmitted. High incidence among homosexuals and drug addicts - increases risk of liver cancer - hepatocellular carcinoma - virus enters through break in skin or mucous membrane or by injection into bloodstream Reaches liver cells, multiplies and releases viruses into blood; average 7 week incubation - most exhibit few overt symptoms and eventually develop HBV immunity - some patients experience malaise, fever, chills, anorexia, abdominal discomfort, and diarrhea - fever, jaundice, rash, and arthritis in more severe cases - small number of patients develop chronic liver disease - necrosis and cirrhosis - characteristics: DNA virus, has an envelope, chronic carrier, transmission through blood, semen, and sexual contact, 1-6 month incubation period, fever, rash, arthritis, jaundice,

Answer 36

Diagnosis based on examination of risk factors, serological tests to detect viral antibodies or antigen; radioimmunoassay and ELISA tests for surface antigen Screening of blood transfusion, semen for sperm banks, organs for transplant, and routine prenatal testing of all pregnant women Mild cases managed by treatment of symptoms and supportive care; chronic infections treated with interferon Prevention: passive immunization with HBIG for persons exposed, or possibly exposed, including neonates born to infected mothers - primary prevention is vaccination for high risk individuals and encouraged for all newborns and infants - vaccine derived from surface antigen from cloned yeast - 3 doses with boosters - vaccine derived from purified sterile antigen extracted from carrier blood; mainly for people who have yeast allergies

Answer 37

Acute and spreads fecal-orally

Answer 38

Spread by blood and fluids - chronic - cirrhosis and cancer

Answer 39

Non-enveloped segmented dsRNA viruses - unusual double stranded RNA genome Two best known: 1. Reovirus: cold-like upper respiratory infection enteritis 2. Rotavirus: oral-fecal transmission; primary viral cause of mortality and morbidity resulting from diarrhea in infants and children #1 Primary Cause of Diarrhea in infants/children and death from these diarrheal disease (500,00 a year) In the US, Rotavirus used to be primary cause of infant hospitalizations - Rotateq and Rotarix - attenuated vaccine

Answer 40

Non-enveloped Nonsegmented ssRNA Viruses - Norwalk sheet best known; Noroviruses believed to cause 1/3rd of all viral gastroenteritis cases (20 million/yr) - Currently these are described as Noro-like viruses (NLVs) - Transmitted by fecal-oral route - infections in all ages at any time of the year - acute onset, nausea, vomiting, cramps, diarrhea, chills - Dr. L’s description, “violent both ender” - rapid and complete recovery *Cruise Ship Virus - boats have been quarantined (long before COVID-19) as a consequence of recurrent outbreaks *Hep E used to be considered a Calci Virus

Answer 41

Non-enveloped nonsegmented ssRNA - are named for their small (Pico) size and their RNA core Large family of viruses significant to human health (the “herpes” of the RNA chart). Many emerging threats D68 are picornaviruses Important genera - Enterovirus: poliovirus, HAV - Rhinovirus - Cardiovirus: infects heart and brain

Answer 42

Enteroviruses: general features - Entero: fecal-oral transmission, indirect fomite transmission - poor quality increases risk - general unhygienic living increase risk

Answer 43

Poliomyelitis (polio): acute enteroviral infection of the spinal cord that can cause neuromuscular paralysis Poliovirus: naked capsid; resistant to acid, bile, and detergents; can survive stomach acids when ingested *worldwide vaccination programs have reduced the number of cases; eradication is expected

Answer 44

Transmitted by fecal-oral route - polioviruses adhere to receptors of mucosal cells in oropharynx and intestine, multiply in number and shed in throat and feces - some virions leak into blood - most infections are short term, mild viremia - some develop mild nonspecific symptoms of fever, nausea, sore throat, myalagia - if viremia persists, virus spreads to spinal cord and brain - if nervous tissue is infected but not destroyed - muscle pain and spasm, meninges inflammation, and vague hypersensitivity - invasion of motor neurons causes flaccid paralysis - decades later post-polio syndrome (PPS) - progressive muscle deterioration; occurs in 25%-50% of patients infected with poliovirus in childhood - 90% asymptomatic

Answer 45

Paralysis of the muscles of the legs, abdomen, and back, intercostals, diaphragm, pectoral girdle, and bladder can result Bulbar poliomyelitis - rare cases, requires mechanical respirators - brain stem, medulla, or cranial nerves affected Severe deformities of the trunk and limbs develop follows muscle atrophy - spine, shoulder, hips, knees, feet

Answer 46

Treatment is largely supportive for pain and suffering; respiratory failure may require artificial ventilation; physical therapy may be needed Prevention is vaccination - inactivated polio vaccine - Salk Vaccine - oral polio vaccine, Sabin vaccine, attenuated virus, - no longer recommended in the US - worldwide eradication is being attempted

Answer 47

Coxsackieviruses: hand-foot-mouth disease

Answer 48

Cubical Picornaviruses relatively resistant to heat and acid Not carried chronically (acute infections), principal reservoirs are asymptomatic, short-term carriers or people with clinical disease - fecal-oral transmission; multiplies in small intestine and enters the blood and is carried to the liver - most infectious subclinical or vague, flu-like symptoms occur; jaundice is seldom present Treatment: no specific treatment once the symptoms begin Prevention - vaccination - inactivated of attenuated viral vaccines - pooled immune serum globulin for those entering into endemic areas or post known exposure - clean water and hygiene

Answer 49

- more than 110 serotypes associated with the common cold - unique molecular surface markers makes development of a vaccine unlikely - many strains circulating in the population at one time; acquired from contaminated hands and fomites - sensitive to acidic environments; optimum temperature is 33 degrees Celsius - symptoms: headache, chills, fatigue, sore throat, cough, nasal drainage - treatment: treat the symptoms - handwashing and care in handling nasal secretions

Answer 50

Viruses spread by arthropod vectors - arthropod vectors: mosquitoes, ticks, flies, and gnats - 400 viruses - toga viruses, flaviviruses, some bunyaviruses, and reoviruses - most illnesses caused by these viruses are mild fever; some may cause severe encephalitis, and life-threatening hemorrhagic fever

Answer 51

Dengue fever: flavivirus carried by Aedes mosquitoes; not in US - usually mild infection - dengue hemorrhagic shock syndrome (breakbone fever) - extreme muscle and joint pain; can be fatal

Answer 52

- vectors and viruses tend to be clustered in the tropics and subtropics; many temperate zones have periodic epidemics - arbovirus life cycles are closely tied to the ecology of the vectors - infections show a peak incidence when the arthropod is actively feeding and reproducing - humans can serve as dead-end, accidental hosts or they can be a maintenance vector *controlling the vector controls the disease

Answer 53

Arboviruses - the wrapping (envelope) needs protection in the vector as it moves around new hosts. Human are accidental, dead-end hosts for these viruses w Chikungunya: native transmission in the US started in 2014 - fever and joint pain

Answer 54

German measles - endemic disease - most cases reported are adolescents and young adults - transmitted through contact with respiratory secretions - diagnosis based on serological testing - no specific treatment available - attenuated viral vaccines MMR - the R in the MMR Two clinical forms 1. Postnatal rubella: malaise, fever, sore throat, lymphadenopathy, rash, generally mild, lasting about 3 days 2. Congenital rubella: infection during 1st trimester most likely to induce miscarriage or multiple defects such as cardiac abnormalities, ocular lesions, deafness, mental and physical retardation

Answer 55

West Nile Virus Encephalitis: transferred to humans by mosquitoes infected by birds blood - 80% of people infected show no symptoms; less than 1% develop neurological illness (encephalitis or meningitis) Zika Virus: symptoms very similar to infection with chikungunya or dengue viruses. Birth defects of mother infected during pregnancy Dengue fever: flavivirus carried by Aedes mosquitoes; usually mild infection - it’s the second time that gets you (strain matters) - dengue hemorrhagic shock syndrome (breakbone fever) - extreme muscle and joint pain; can be fatal

Answer 56

Acquired through blood contact - blood transfusions, needle sharing by drug absusers - more common to have chronic liver disease, without overt symptoms - cancer may also result from chronic HCV infection Treatment - depends on viral genotype - genotype 1 - sofosbuvir and ledipasvir for 12 weeks - other genotypes are usually treated for 12 weeks with sofosbuvir, coupled with velpatasvir Previously - with interferon and ribavirin to lessen liver damage; no cure and no vaccine

Answer 57

- Relatively large RNA viruses with distinctively spaced spikes on their envelopes - common in domesticated animals - 5 types of human coronaviruses have been characterized, among these are agents of… Common Cold - some forms of viral pneumonia and myocarditis - some human enteric infections - severe acute respiratory syndrome (SARS): airborne transmission - 9% of cases fatal - middle eastern respiratory syndrome - 40% of cases fatal

Answer 58

SARS and MERS - transmitted through droplet or direct contact - fever, body aches, malaise - may or may not experience respiratory symptoms with breathing problems; severe cases can result in respiratory distress and death - treatment is supportive

Answer 59

Two phases 1. Host responds to virus 2. Host responds to own inflammatory response - not everyone with virus reaches this stage

Answer 60

- convert ssRNA into dsDNA using reverse transcriptase - dsDNA integrates into host cell genome and serves as a template for mRNA synthesis and genome synthesis

Answer 61

Human immunodeficiency virus (HIV) - acquired immunodeficiency syndrome - first emerged in early 1980s - severe pneumonia caused by Pneumocystis jirovecii (ordinarily a harmless fungus) - a rare vascular cancer called Kaposi Sarcoma - sudden weight loss, swollen lymph nodes - general loss of immune function - 1959 first documented case of AIDS

Answer 62

HIV-1 and HIV-2 - T-cell lymphotropic viruses 1 and II - leukemia and lymphoma - HIV can infect host cells that have the required CD4 marker + a co-receptor

Answer 63

Transmission occurs by direct and specific routes - mainly through sexual intercourse and transfer of blood or blood products - babies can be infected before or during birth, and from breast feeding - HIV does not survive long outside the body - first nationally notifiable in 1984 - 6th most common cause of death among people aged 25-44 years in the US - men account for 75% of new infections - IV drug abusers can be HIV carriers; significant factor in spread to heterosexual population - in 2009, the number of infected individuals worldwide is estimated to be 35 million with 1.2 million in the US

Answer 64

Pathology tied to two factors 1. The level of viruses 2. The level of T cells in the blood primary effects of HIV infection - extreme leukopenia -lymphocytes in particular formation of giant T cells and other syncytia virus spreads - infected macrophages release the virus in CNS, with toxic effect, inflammation Secondary effects of HIV - CD4 lymphocytes destruction - opportunistic infections and malignancies during full-blown AIDS

Answer 65

Testing based on detection of antibodies specific to the virus in serum or other fluids; done at 2 levels Initial screening - ELISA, latex agglutination, and rapid antibody tests - Rapid results but may result in false positives Follow up with western blot analysis to rule out false positives False negatives can occur; persons who may have been exposed should be tested a second time 3-6 months later

Answer 66

No vaccine - monogamous sexual relationships - condoms - universal precautions No cure; therapies slow down the progress of the disease or diminish the symptoms - inhibit viral enzymes: RT, protease, integrase - inhibit fusion - inhibit viral integration - highly active anti-retro viral therapy (most effective) HAART therapy

Answer 67

Transmitted zoonotically; cause periodic epidemics; extremely dangerous; bio safety level 4 Bunyaviruses - typically transmitted by insects and ticks - California encephalitis, rift valley fever, Korean hemorrhagic fever - American bunyavirus is a hantavirus, Sin Nombre - hantavirus pulmonary syndrome (HPS) emerging disease; high fever, lung, edema, and pulmonary failure; 33% mortality rate - carried by deer and harvest mice; transmitted via airborne dried animal waste Arenavirus - Lassa fever, Argentine hemorrhagic fever, blovian hemorrhagic fever, and lymphocytic chorionmeningitis - closely associated with rodent host - transmission through aerosols and contact

Answer 68

Rhabdovirus family; genus lyssavirus Enveloped, bullet-shaped virions Slow, progressive zoonotic disease Primary reservoirs are wild mammals; it can be spread by both wild and domestic mammals by bites, scratches, and inhalation of droplets Virus enters through bite, grows at trauma site for a week and multiplies, then enters nerve endings and slowly advances toward the ganglia, spinal cord and brain Infection cycle completed when virus replicates in the salivary glands Clinical phase of rabies: - prodromal phase - fever, nausea, vomiting, headache, fatigue; some experience pain, burning, tingling sensations at site of wound - furious phase - agitation, disorientation, seizures, twitching, hydrophobia - dumb phase - paralyzed, disoriented, stuporous - progress to comma phase, resulting in death

Answer 69

Often diagnosed at autopsy - intracellular inclusions (Negri bodies) in nervous tissue Bite from wild or stray animals demands assessment of the animal, meticulous wound care, and specific treatment Preventive therapy initiated if signs of rabies appears Treatment - passive and active post exposure immunization - infuse the wound with human rabies immune globulin (HRIG) and globulin; vaccination with human diploid cell vaccine (HDCV), an inactivated vaccine given in 6 doses with 2 boosters Control - vaccination of domestic animals, elimination of strays, and strict quarantine practices - live oral vaccine incorporated into bait for wild animals

Answer 70

Ebola - BSL4, hemorrhagic fever - describes the severe, multi system syndrome seen in Ebola epidemics - host vascular system is damaged, so vascular leakage of fluids is accompanied by diminished clotting ability

Answer 71

F-protein: fascilitastes fusion of virus with cell, but will also result in cells fusing together. Forms syncytium or giant multi-nucleated cells - Four important paramyxoviruses - parainfluenza - Croup - mumps - measals - RSV - respiratory syncytial virus

Answer 72

Widespread as influenza but more benign Respiratory transmission Seen mostly in children - primary infection in infants can be severe to be life-threatening Characteristic “seal-bark” cough, “croup” cough Minor cold, bronchitis, bronchopneumonia, coup No specific treatment available; supportive therapy; cool, dry air

Answer 73

Epidemics parotitis: self-limited illness, associated with painful swelling of parotid salivary glands - humans are the only reservoir - 40% of infections are subclinical; long-term immunity - 300 cases in US/year - incubation 2-3 weeks fever, muscle pain, and malaise, classic swelling of one or both cheeks - usually uncomplicated invasion of other organs; in 20-30% of infected adult males, epididymis and testes become infected; sterility is rare - symptomatic treatment - live attenuated vaccine MMR

Answer 74

Also known as red measles and rubeola - different from German measles - very contagious; transmitted by respiratory aerosols - humans are the only reservoir - less than 100 cases/yr in US, frequent cause of death worldwide Virus invades the mucosal lining of respiratory tract Initial symptoms - sore throat, dry cough, headache, conjunctivitis, lymphadenitis, fever Koplik’s spots: oral lesions Exanthem: characteristic red maculopapula eruption on the head, progressing to trunk and extremities to cover most of the body

Answer 75

Most serious complication is subacute sclerosing panendephalitis (SSPE), a progressive neurological degeneration of the cerebral cortex, white matter, and brain stem - 1 case in a million infections - involves a defective virus spreading through the brain by cell fusion and destroys cells - leads to coma and death in months or years Attenuated viral vaccine: MMR

Answer 76

Infects upper respiratory tract and produces giant multinucleate cells Most prevalent cause of respiratory infection in children 6 months or younger; most susceptible to serious disease - epithelia of nose and eye portal of entry; replicates in nasopharynx - fever, rhinitis, pharyngitis, otitis, croup Treatment: - synagis, a monoclonal antibody that blocks attachment to cells, RSV immunoglobulin - prophylaxis for exposed children - ribavirin, inhaled antiviral drug

Answer 77

3 distinct influenza virus types: A, B, C *Type A causes most infections Influenza nomenclature chronicles virus type, animal of origin, location, and year of origin 1. Influenza A: after 2003, strains of this virus that usually infects birds underwent an antigenic shift and began to infect humans 2. Influenza B: only undergo antigenic drift, no antigenic shift 3. Influenza C: known to cause only minor respiratory disease; probably not involved in epidemics

Answer 78

- acute, highly contagious respiratory illness - seasonal, pandemics; among top 10 causes of death in Us - most commonly among elderly and small children - binds to ciliated cells of respiratory mucosa - causes rapid shedding of cells, stripping the respiratory epithelium; severe inflammation - fever, headache, myalgia, pharyngeal pain, shortness of breath, coughing - weakened host defenses predispose patients to secondary bacterial infections, especially pneumonia

Answer 79

Virus attaches to, and multiplies in cells if respiratory tract, segments of RNA genome enter the nucleus, finished viruses are assembled and bud off the cell

Answer 80

Key to influenza are glycoproteins spikes - Hemagglutination (H): 15 subtypes; most important virulence factor; binds to host cell - Neuraminidase (N): 9 subtypes - hydrolyzes mucus and assists viral budding and release Both glycoproteins frequently undergo genetic changes, decreasing (not eliminating) the effectiveness of the host immune response

Answer 81

Constant mutation is called antigenic drift - gradually change their amino acid composition Antigenic shift: one of the genes or RNA strands is substituted with a gene or strand from another influenza virus from a different animal host - genome of virus consists of 10 genes encoded on 8 separate RNA strands - requires co-infection with two strains of virus

Answer 82

Diagnosis: - rapid immunofluorescence tests to detect antigens in a pharyngeal specimen - serological testing to screen for antibody titer Treatment: - control symptoms; amantadine, rimantadine, zanamivir (relenza), and oseltamivir (tamiflu) - flu virus has developed high rate of resistance to amantadine and rimatadine Annual vaccine recommended