S1B4 - RNA viruses Flashcards
What are the three most common causes of aseptic meningitis?
The three most common causes of aseptic meningitis include
- Coxsackievirus
- Echovirus
- Mumps
What is the function of neuraminidase in the context of influenza?
Neuraminidase (NA) envelope protein cleaves HA-sialic acid interaction during budding to permit viral spread.
Describe the progression and appearance of the rash in measles.
The exanthem of measles infection is a maculopapular, blanching rash that appears a few days after the prodrome phase, and begins on the face and spreads centrifugally to involve the body and extremities.
What can be given as prophylaxis for immunocompromised patients at risk for severe RSV infection?
Palivizumab (blocks fusion protein F) can be used for prophylaxis in immunocompromised patents at risk for severe RSV infection.
Replication and transcription of rabies virus occurs in Negri bodies, which are pathognomonic of rabies infection. Negri bodies are cellular inclusion bodies which are…
- eosinophilic or basophilic?
- intranuclear or intracytoplasmic?
- found in neuron cell bodies in the spinal cord and CNS — especially in which 2 specific locations?
Replication and transcription of rabies virus occurs in eosinophilic cytoplasmic inclusions called Negri bodies within neuron cell bodies in the spinal cord and CNS (especially Purkinje cells in the cerebellum and pyramidal cells of the hippocampus).
Describe the basic virology of hantavirus (capsid symmetry, enveloped/nonenveloped, segmented/unsegmented, and genetic material). To which virus family does Hantavirus belong?
Hantavirus (Sin Nombre) is an enveloped, helical capsid virus with a negative-sense/ambisense, segmented single-stranded RNA (ssRNA) bunyavirus.
What are the presenting symptoms in a patient with hepatitis A?
Patients initially present with a prodromal stage (i.e. fever and flu-like symptoms), often progressing to the icteric stage (i.e. bilirubinuria, pale stools, and jaundice).
What are Cowdry Type A bodies composed of? What group of viruses is this specific to?
Cowdry Type A bodies are eosinophilic nuclear inclusions composed of nucleic acid and protein seen in cells infected with organisms within the herpesvirus family.
Describe the characteristics and classification of the virus causing Hepatitis A infection. How is it transmitted? Does it cause acute or chronic hepatitis?
HAV is a picornavirus that is transmitted fecal-oral and causes acute hepatitis (no chronic carrier state) that may be anicteric. HAV is commonly acquired by travelers.
What is the treatment for a mumps infection?
Treatment for mumps infection is supportive.
What disease does rotavirus cause?
Rotavirus is the most common cause of viral gastroenteritis in infant/young children (both fatal and non-fatal).
ROTA: “Right Out The Anus”
A 10-year-old boy who has an obsession with hamsters presents to the emergency department with an influenza-like symptoms, along with signs of meningismus. Hantavirus is ruled out of the differential diagnosis, but based on CSF results a viral etiology is suspected. What other causative virus could be responsible for this patient’s presentation?
Lymphocytic choriomeningitis virus (LCMV) is a rodent-borne arenavirus transmitted by exposure to the urine and feces of rodents, including mice and hamsters. Affected patients generally present with an influenza-like systemic illness accompanied by headache and meningismus.
Hepatitis E virus is endemic in what geographic areas?
HEV is endemic in Africa, Asia, and the Middle East.
What virus is responsible for SARS?
Severe acute respiratory syndrome (SARS) is caused by a certain strain of coronavirus.
Synthesis of what factor leads to the coagulation defects seen in Ebola virus infection?
Coagulation defects in Ebola virus infection occurs indirectly through the synthesis of tissue factor, which triggers the extrinsic coagulation pathway. In addition, the proinflammatory cytokines induce macrophage production of tissue factor.
What are some risk factors that may put you at risk for an Ebola virus infection?
Risk factors include recent travel to an African region where Ebola virus outbreaks have occurred, laboratory accident when working with Ebola, or illness in a healthcare worker during an epidemic in Africa.
In what virus family is Human T-cell lymphotropic virus?
What are some unique things about Human T-cell lymphotropic virus?
Human T-cell lymphotropic virus is in the retrovirus family.
- Able to immortalize or transform host cells; not cytolytic
- Transmission:
- HTLV-1 via milk and blood (found in Caribbean, Japan, South America, Africa);
- HTLV-2 via blood (geographic distribution is unclear.
- Presentations:
- asymptomatic infections (most common)
- Tropical spastic paraparesis (HTLV-1)
- Adult leukemia (acute T-cell lymphocytic leukemia, ALT) (HTLV-1) Non-hodgkin’s lymphoma
How is RSV transmitted?
Transmission of RSV occurs from respiratory droplets.
What is the mode of transmission for rotavirus?
Rotavirus has a fecal-oral transmission (common in preschools and day care centers).
Can you name 1 virus family which is nonenveloped with icosahedral capsid symmetry and contains dsRNA?
An example of a nonenveloped, icosahedral capsid, dsRNA virus is the reovirus family. Examples include rotavirus and Colorado tick fever virus.
How is measles diagnosed?
Diagnosis of measles is made via serology.
Most often by clinical presentation alone. Seroconversion, immuno-based or viral RNA tests are useful. Giant cells can be observed in tissue samples.
How does parainfluenza infection manifest in adults?
Parainfluenza infection in adults usually presents as a severe cold with nonspecific findings such as
- Fever
- Rhinorrhea
- Cough
- Sore throat
How is mumps virus transmitted?
Transmission of mumps virus occurs via respiratory droplets.
What is the pattern of rash progression seen in rubella?
The rash starts on the face and progresses down to extremities, just like with measles.
How is rubella different than other togaviruses?
Unlike other togaviruses, rubella is not an arbovirus because it is not transmitted by an arthropod.
What are the main vectors for Rabies virus in the United States?
The transmission of rabies in the United States is mainly due to bats overall, with skunks common in the west, and raccoons/foxes in the east. Another disease caused by bats (and birds) that can be problematic for cave explorers is the fungus Histoplasma capsulatum.
What complications are associated with hepatitis A?
HAV may result in complications such as:
- Prolonged or relapsing symptoms
- Acute liver failure
- Death (more likely in patients with concomitant Hepatitis C infection, or in the elderly)
Patients do not develop chronic liver disease as a result of hepatitis A.
What are some complications experienced by neonates born to mothers infected by rubella:
- heart?
- eyes?
- CNS?
- skin?
- bones?
- head size — big or small?
Congenital rubella occurs when a pregnant woman is infected with rubella during the first trimester, and the virus infects fetal cells transplacentally.
The classic triad of congenital rubella includes:
- Patent ductus arteriosus (PDA)
- Cataracts
- Sensorineural deafness
Heart defects:
- PDA (patent ductus arteriosus)
- Pulmonary artery stenosis/hypoplasia
Eye defects:
- Cataracts (white pupils)
- Microphthalmia
- Glaucoma
- Pigmented retinopathy
CNS defects:
- Sensorineural deafness
- Mental retardation
Skin and musculoskeletal defects:
- Purpuric “blueberry muffin” rash (dermal erythropoeisis) — may also be seen in congenital CMV
- Radiolucent bone lesions — vs. the metaphyseal dystrophy and periostitis characteristic of congenital syphilis
Other defects:
- Microcephaly — vs. the macrocephaly characteristic of congenital toxoplasmosis
- Hepatosplenomegaly
- Thrombocytopenia
A 45-year old woman complains of fatigue and abdominal pain. She has a normal diet, and has recently lost some weight. Upon questioning, she reveals that she is an alcoholic, and has been trying to decrease her drinking. On abdominal exam, the liver is firm and enlarged. An abdominal CT reveals hepatocellular carcinoma. What addition to the patient’s history would multiply the patient’s risk for this disease?
A) IV drug use
B) Pancreatitis
C) Recent travel
D) Crohn’s disease
A) IV drug use
The combination of alcoholic cirrhosis and hepatitis C virus infection multiplies a patient’s risk for hepatocellular carcinoma. Since hepatitis C is frequently transmitted through IV drug use, the addition of this information to the history would increase the likelihood of hepatocellular carcinoma.
In what virus family is astrovirus?
What makes it different from other viruses in that family?
What is the common disease of this virus?
- astrovirus is in the calcivirus family
- astroviruses resemble Norovirus with their five to six-pointed star-shaped capsomers but they lack the cup-shaped morphology
- Epidemic viral gastroenteritis also called summer diarrhea
What patient population has an increased risk of developing fulminant hepatic failure as a result of hepatitis E infection?
For unknown reasons, pregnant woman in their third trimester have an increased risk of developing fulminant hepatic failure following Hepatitis E infection.
Describe the pathophysiology of mumps virus once it attaches to the respiratory tract epithelium.
Mumps virus attaches and invades the upper respiratory tract epithelium via viral hemagglutinin envelope proteins leading to viremia. After a 2-3 week incubation period, the virus can cause inflammation and edema of glandular tissue along with spread to the meninges.
Describe the 4 symptoms of rubeola infection after the initial prodrome of fever, malaise, and anorexia.
The prodrome phase in a measles (rubeola) infection presents with fever, malaise, and anorexia, followed by the 4C’s of measles:
- Conjunctivitis
- Cough
- Coryza (rhinitis)
- Koplik’s spots
How does an initial infection from Hepatitis C present?
HCV infects hepatocytes and can present with acute hepatitis that presents as jaundice and fever from the destruction of infected hepatocytes by cytotoxic T cells.
(similar initial presentation to HepA)
Which 4 RNA viruses cause hepatitis?
The main RNA viruses that cause hepatitis include
- Hepatitis A (HAV)
- Hepatitis C (HCV)
- Hepatitis D (HDV)
- Hepatitis E (HEV)
Remember, HBV is a DNA virus.
Herpesviruses: Describe their capsid symmetry, envelope, and genetic material.
Herpesvirus are a group of icosahedral, enveloped capsid herpes viruses with linear double-stranded DNA (dsDNA).
What type of antigenic variation is responsible for pandemics in influenza?
Antigenic shifts are caused by the exchange of RNA segments between human and animal viruses that lead to radically new HA or NA, causing pandemics.
Picornaviruses, caliciviruses, and hepeviruses have what capsid, envelope, and genomic characteristics?
Nonenveloped, icosahedral capsid, (+) sense ssRNA viruses:
-
Picornaviruses: The smallest RNA viruses, divided into two groups.
- Enteroviruses: Poliovirus, Coxsackie virus, echovirus, hepatitis A
- Rhinoviruses
-
Calicivirus:
- Norovirus
-
Hepevirus:
- Hepatitis E virus
What type of vaccine is available for measles?
A live-attenuated measles-mumps-rubella (MMR) vaccine is available.
What is the incubation period of rubella?
Rubella infection from aerosol transmission infects the nasopharynx and has an incubation period of 14-21 days, where the virus replicates in local lymph nodes.
What is the typical presentation in patients with hepatitis E infection?
Patients typically present with 2 phases of symptoms, the prodromal phase and the icteric phase.
Prodromal symptoms include:
- Myalgias
- Mild fever
- Right upper quadrant pain
- Nausea/vomiting
- Weight loss
- Anorexia
Icteric phase symptoms include:
- Light colored stools
- Jaundice
- Pruritis
In what viral family is the Colorado tick fever virus?
What are some interesting Colorado tick fever facts?
Colorado tick fever virus is in the reovirus family.
- one of the most common tick-borne diseases in the USA
- usually a mild disease but can be severe in children
A 5 year old female presents with fever, a “barking seal” cough, inspiratory stridor and this chest radiograph. What is the most likely diagnosis and etiology?
Diagnosis: Croup
Etiology: Parainfluenza virus
Parainfluenza infection in children leads to croup (laryngotracheobronchitis) and pneumonia.
Croup is characterized by the degree of airway obstruction but usually involves
- Fever
- Hoarseness
- Barking (“seal-like”) cough upon expiration
- Inspiratory stridor
X-ray shows the “steeple sign”.
What is the clinical presentation of croup?
Croup is characterized by the degree of airway obstruction but usually involves
- Fever
- Hoarseness
- Barking (“seal-like”) cough upon expiration
- Inspiratory stridor
What are some of the clinical manifestations of influenza and the complications associated with influenza?
Influenza causes:
- Flu
- Croup in children
- Secondary bacterial pneumonia
- CNS involvement (encephalopathy, encephalitis, transverse myelitis, aseptic meningitis, and Guillain-Barré syndrome)
- Myositis and rhabdomyolysis
- Cardiac complications
- Toxic shock syndrome
How are the different strains of Influenza named?
Influenza viruses are named based on HA and NA types (i.e. H5N1).
What is the pathogenesis behind the symptoms of inflammation and fever in influenza?
Replication within cells eventually leads to cell lysis and necrosis of the epithelium, leading to leakage of intracellular contents that stimulates inflammation and fever.
Name three viral families where you are likely to see multinucleate giant cells (bonus: name the individual viruses)
Multinucleated giant cells are seen in
- Herpesvirus (HSV-1, HSV-2, and VZV)
- Retroviruses
- Paramyxoviridae (RSV, parainfluenza virus, mumps, and measles) due to the F (fusion) protein
How is diagnosis of calicivirus infection made?
Diagnosis of calicivirus infections can be based on clinical manifestations, however clear diagnosis is made via reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA).
Coronaviruses have what capsid, envelope, and genomic characteristics?
Enveloped, helical capsid, (+) sense ssRNA:
- *Coronavirus**:
- Coronavirus
- SARS
What is the only family of double-stranded RNA virus. Describe its capsid, envelope, and genetic material.
Respiratory Enteric Orphan viruses, more commonly referred to as Reoviruses, have an icosahedral capsid, nonenveloped, segmented double-stranded (ds) RNA (10-12 segments).
Reoviruses make up 1 of 4 non-enveloped RNA viruses (Picornavirus, Calicivirus, Reovirus, Hepatitis E) and can withstand the harsher conditions of the digestive tract.
What are the paramyxoviruses and and what is their basic viral morphology?
Enveloped, helical capsid, (-) sense ssRNA viruses:
Paramyxovirus:
- Parainfluenza
- RSV (respiratory syncytial virus)
- Mumps
- Measles
- hMNV (human metapneumovirus)
A young child has viral pneumonia—what are the 3 most likely causes?
The most common causes of pneumonia in young children in descending order include
- RSV
- Human metapneumovirus (hMPV)
- Parainfluenza virus
Describe the basic virology of RSV (capsid symmetry, enveloped/nonenveloped, and genetic material).
Respiratory Syncytial Virus (RSV) a helical, enveloped capsid virus with a negative single-stranded RNA (ssRNA) paramyxovirus.
Which hepatitis virus causes significantly higher mortality rates during pregnancy? What virus family is it from?
HEV is a hepevirus that is transmitted fecal-oral and causes acute hepatitis. HEV infection in pregnant women is associated with fulminant hepatitis, and is commonly acquired from contaminated water or undercooked seafood.
Is hantavirus classified as an arbovirus or a robovirus?
What is the reservoir for hantavirus in the U.S.?
Unlike other Bunyavirudae, hantavirus is an example of a ROBOvirus (ROdent-BOrne virus), as opposed to an ARBOvirus (ARthropod-BOrne virus). In the U.S., the primary reservoir for hantavirus is the deer mouse.
Arenaviruses and bunyaviruses have what capsid, envelope, and genomic characteristics?
Enveloped, helical capsid, (-) sense/ambisense* ssRNA:
[*Note: In this context, ambisense means RNA segments that contain both + and – polarity]
-
Arenavirus:
- Lassa Fever virus
- LCM (Lymphocytic choriomeningitis)
-
Bunyavirus:
- Hantavirus
- California EV (encephalitis virus)
- Rift Valley fever
- Sandfly fever
Describe the cardiopulmonary manifestation of hantavirus cardiopulmonary syndrome (HCPS). What radiographic finding of the lungs does HCPS resemble?
Hantavirus cardiopulmonary syndrome (HCPS) denotes the capillary leak into the pulmonary bed after a flu-like prodrome phase. Patients present with fever and bilateral diffuse interstitial edema that radiographically resembles adult respiratory distress syndrome (ARDS).
Herpes viruses are known for establishing lifelong latent infection (“the gift that keeps on giving”). However, different herpesviruses remain latent in different cell types. Where do HSV, VZV, EBV, and CMV reside during their latent phase?
Herpesvirus: Location of latency
HSV-1 - Trigeminal nerve ganglion
HSV-2 - Sacral nerve ganglion
VZV - Any sensory ganglion
EBV - B-cells
CMV - Lymphocytes (persistent infection in monocytes and macrophages)
What are the arboviruses?
Arboviruses include viruses from families that can be remembered by “Remember, Fleas, Ticks, and Bugs!”
- Reoviruses
- Flaviviruses
- Togaviruses
- Bunyaviruses
Which family of viruses derive their membranes from the host cell nuclear membrane?
Herpesviruses have envelopes derived from the budding of nuclear membrane. Contrast this with the cytoplasmic membrane, because assembly occurs in the nucleus.
Fatal outcomes from Ebola virus infection usually occurs because of what pathological causes?
Fatal outcomes associated with Ebola virus usually occur due to severe intravascular volume depletion, metabolic abnormalities, and impaired oxygen delivery.
What is the incubation period for Ebola?
Incubation period is usually about five to seven days, but in some cases may exceed two weeks.
(5-7 days in First-Aid, 5-10 days in NS handout, 10 days in Picmonic)
Where does replication of influenza virus occur within the cell?
Replication occurs within the nucleus, which is unique among RNA viruses. Orthomyxoviruses and retroviruses are the only RNA viruses that replicate within the nucleus.
What is the general pathogenesis of Hepatitis D?
HDV is a delta virus that is transmitted parenterally and requires HBV HBsAg. Superinfection occurs upon an existing HBV infection and is more severe than co-infection (an infection with HBV and HDV at the same time).
How is measles transmitted?
Transmission of measles is highly contagious and occurs from person-to-person contact of respiratory droplets.
What is the mechanism behind rotavirus’s ability to cause viral gastroentiritis? Is the gastroenteritis bloody or non-bloody?
Rotavirus contains a viral encoded non-structural protein (NSP4) which acts as an enterotoxin, causing non-bloody (non-inflammatory), watery diarrhea leading to dehydration, and death (without rehydration).
How long does the rash usually last in rubella?
The rash from rubella infection is usually evident for 3 days.
What are risk factors associated with contracting the hepatitis A virus?
The U.S. has a much lower incidence of the virus compared to Mexico and Central/South America. Other risk factors for contracting the virus (besides foreign travel) include:
- Personal contact
- Consumption of shellfish
- Day-care centers
- Institutionalization (e.g. prisoners)
- Male homosexuality
What is the only natural host for the rubella virus?
Humans are the only natural host of the disease and large scale vaccination with the measles, mumps, rubella (MMR) vaccine has led to the elimination of the virus in the United States.
What are the possible complications of hepatitis E infection?
HEV may result in complications such as encephalopathy, disseminated intravascular coagulation (DIC), and fulminant hepatic failure.
Following inoculation, what host cell surface receptor does rabies virus bind?
Rabies virus glycoprotein initially bind to nicotinic acetylcholine receptors (nAchRs) in the postsynaptic muscle membrane of the neuromuscular junction.
Describe the basic virology of caliciviruses (capsid symmetry, enveloped/nonenveloped, and genetic material).
Caliciviruses (Norwalk virus, Norovirus): (+) ssRNA, nonenveloped, icosahedral, fecal-oral transmission.
Caliciviruses are 1 of 4 non-enveloped RNA viruses (Picornavirus, Calicivirus, Reovirus, Hepatitis E).
What are the most common “common cold” viruses?
The “common cold” can be caused by many different viruses, the most common being:
- Rhinovirus
- Coronavirus
- Adenovirus
- Influenza C virus
- Coxsackievirus (A and B)
A homeless woman with no known medical or vaccination history gives birth to a boy with intrauterine growth retardation, “blueberry muffin” rash, cataracts, and continuous machine-like murmur. What is the most likely diagnosis?
A) Congenital varicella syndrome
B) Congenital syphilis
C) Congenital toxoplasmosis
D) Congenital rubella
D) Congenital rubella
Congenital rubella is classically characterized by cardiac defects (e.g., PDA), cataracts, deafness, and “blueberry muffin” rash.
Congenital toxoplasmosis is characterized by the classic triad of chorioretinitis, intracranial calcifications, and hydrocephalus.
Congenital syphilis is characterized by hydrops fetalis or if born alive, facial anomalies and deafness with more prominent late manifestations.
What percentage of hepatitis C patients become chronic carriers?
HCV infection that is not eliminated (60-80% of cases) can lead to the development of chronic active hepatitis C or an asymptomatic carrier state.
Other than serology, what other laboratory tests aid in the diagnosis of a Hepatitis E infection?
Other helpful laboratory tests include:
- ALT
- AST
- Bilirubin
- Alkaline phosphatase
Elevated (10-20 times normal) aminotransferases are the hallmark in acute viral hepatitis.
What are the top five causes of red rashes in children?
The top 5 causes of red pediatric rashes include:
- Rubella
- Roseola
- Measles
- Scarlet fever
- Parvovirus B19
Mnemonic: Really Red Munchkins Scare Parents.
Flaviviruses, togaviruses, and retroviruses have what capsid, envelope, and genomic characteristics?
Enveloped, icosahedral capsid, (+) sense ssRNA viruses:
- *Flavivirus**:
- Hepatitis C
- Yellow Fever
- Dengue
- WNV (West Nile virus)
- St. Louis EV (encephalitis virus)
Togavirus:
- Rubella virus
- mosquito-borne arboviruses:
– WEE (Western Equine EV (encephalitis virus))
– EEE (Eastern Equine EV)
– VEE (Venezuelan EV)
- *Retrovirus**:
- HIV 1, HIV 2
- HTLV 1, HTLV 2
Treatment for mumps infection is supportive.
Mumps virus is a helical, enveloped capsid virus with a negative single-stranded RNA (ssRNA) paramyxovirus.
What is the only live viral vaccine that can be given to HIV-positive individuals?
MMR is the only live viral vaccine that can be given in HIV-positive individuals.
What is a non-cancerous sequelae of chronic Hepatitis C infection on the liver? And what is the typical length of time for progression?
Chronic disease from HCV may lead to cirrhosis, a process that takes 10-20 years.
What prophylactic measure is available to patients traveling to an area where hepatitis A is endemic?
Vaccination is available for patients prior to traveling to endemic areas.
The disease is usually self-limited and the treatment is generally supportive (i.e. hydration), as most patients (85%) recover completely within 6 months.
After initial infection, how do coagulation defects caused by Ebola virus clinically manifest?
Symptoms persist over a few days before causing signs of hypotension, stupor, and prostration. Coagulation defects usually present as conjunctival hemorrhages, easy bruising, and difficulty to clot after venipuncture - contrary to the accounts of “bleeding from all orifices.”
What is the primary route of infection for the hepatitis A virus?
Hepatitis A (HAV) is one of the more common causes of acute hepatitis. Hepatitis A is caused by a non-enveloped, single-stranded picornavirus. The primary route of infection is almost always fecal-oral, which typically results in bilirubinuria, jaundice, and abdominal pain.
Paramyxoviruses, rhabdoviruses, orthomyxoviruses, and filoviruses have what capsid, envelope, and genomic characteristics?
Enveloped, helical capsid, (-) sense ssRNA viruses:
- *Paramyxovirus**:
- Parainfluenza
- RSV (respiratory syncytial virus)
- Mumps
- Measles
- hMNV (human metapneumovirus)
- *Rhabdovirus**:
- Rabies virus
- Vesicular stomatitis
- *Orthomyxovirus**:
- Influenza A, B, C
- *Filovirus**:
- Ebola virus
- Marburg virus
A newborn presents with sensorineural deafness, a patent ductus arteriosus, cataracts, and generalized petechiae and purpura. The mother states she developed a maculopapular rash during pregnancy that started on her face and then moved to the rest of her body. What is the most likely diagnosis for this child?
Clinical features of congenital rubella syndrome include:
- “Blueberry muffin rash” from petechiae and purpura
- Hepatosplenomegaly
- Sensorineural deafness
- Patent ductus arteriosus
- Cataracts
- Microcephaly and intellectual disability
What are the potential manifestations of a mumps infection?
Mumps virus can cause conditions that can be remembered by the mnemonic “Mumps make your parotids and testes as big as POM-Poms”
- Parotitis
- Orchitis
- Meningitis (aseptic) and encephalitis
- Acute Pancreatitis
Which vitamin can be used to treat children with measles in developing countries?
Treatment for measles is mainly supportive. Vitamin A deficiency has been identified as a risk factor for measles in children. Although the mechanism is unknown, vitamin A can be used for children in developing countries.
How is influenza transmitted and what tissues does influenza preferentially infect?
Transmission of influenza occurs via inhalation of aerosols that initially infects upper and lower respiratory tract ciliated epithelium via HA and NA surface proteins.
What is the basic viral morphology of coronavirus?
Enveloped, helical capsid, (+) sense ssRNA:
Coronavirus:
- Coronavirus
- SARS
What are the functions of the fusion (F) surface protein in paramyxoviruses?
All paramyxoviruses have viral fusion (F) surface proteins, which causes infected cells to form multinucleated giant cells (syncytia) and mediates cell entry.
Rabies virus:
- incubation period? does the location of inoculation matter?
- prodrome?
Incubates for 2-16 wks → nonspecific prodrome (fever, anorexia) w/ exquisitely sensitive nerves at the bite site.
An 80-year-old man develops fever and respiratory symptoms associated with influenza. After initial improvement of his symptoms he relapses with higher fevers, cough, production of purulent sputum, and radiographic evidence of pulmonary infiltrates. What 3 organisms are most likely the cause?
For infections that persist, usually seen in the elderly or immunocompromised, the ciliary columnar epithelial cells can become damaged, impairing normal task of clearing bacteria. This can lead to a secondary bacterial pneumonia, most commonly from
- Staphylococcus aureus
- Haemophilus influenzae
- Streptococcus pneumoniae
How is hepatitis E treated?
Treatment of HEV infection is primarily supportive. Liver transplant is required in patients with fulminant hepatic failure.
What is the function of hemagglutinin in the context of influenza?
Hemagglutinin (HA) envelope protein binds sialic acid on cells, facilitating endocytosis.
What are four symptoms that characterize hemorrhagic fever with renal syndrome stemming from a hantavirus infection?
Hemorrhagic fever with renal syndrome (HFRS) presents with:
- Fever
- Hemorrhage
- Hypotension
- Renal failure
What is the classic triad of congenital rubella?
The classic triad of congenital rubella includes:
- Patent ductus arteriosus (PDA)
- Cataracts
- Sensorineural deafness
What type of vaccine is available for mumps virus? Does this provide life-long immunity?
A live-attenuated measles-mumps-rubella (MMR) vaccine is available and because only one antigenic type exists, the vaccine provides immunity to mumps virus for life.
How does Ebola cause a systemic inflammatory syndrome?
Infection of macrophages and other cells causes release of proinflammatory mediators, cytokines, and chemokines, which causes a systemic inflammatory syndrome.
What cells are infected during the incubation period of a measles virus infection?
During the 8-10 day incubation period, measles virus replicates and lyses respiratory epithelial cells, leading to infection and lysis of reticuloendothelial cells.
What are the common flaviviruses? What is their basic viral morphology?
Enveloped, icosahedral capsid, (+) sense ssRNA
Flavivirus:
- Hepatitis C
- Yellow Fever
- Dengue
- WNV (West Nile virus)
- St. Louis EV (encephalitis virus)
A 6 year old male presents looking like this. Blood testing reveals elevated serum amylase and leukopenia with a relative lymphocytosis.. What is the likely diagnosis and etiology?
Diagnosis: Mumps
Etiology: Mumps virus, which is a Paramyxovirus
Diagnosis of mumps is based on clinical features if an individual presents with parotitis. Blood testing may reveal elevated serum amylase and leukopenia with a relative lymphocytosis.
What surface protein allows RSV to attach to bronchiolar and alveoli epithelium?
RSV attaches to bronchiolar and alveoli epithelium via protein G (not HA or NA), leading to necrosis and inflammation of bronchioles and alveoli.
What can infection with rabies virus ultimately lead to? How can rabies virus eventually be spread to other individuals?
Rabies virus can eventually:
- Spread to the brain causing rapidly fatal encephalitis.
- Travel down peripheral nerve axons, where large amounts of virus can be shed into the saliva of salivary glands and the secretions of other organs (e.g., intestine) causing spread through aerosols or bites.
What disease does RSV primarily cause in infants?
RSV causes lower respiratory tract disease such as infant bronchiolitis and is the most important cause of infant pneumonia.
What is the typical presentation of rubella?
After incubation, rubella presents with prodrome (malaise, low-grade fever), then the development of a maculopapular rash. There is also an association with non-exudative conjunctivitis and forschheimer spots (patchy erythema on soft palate)
Which non-serological laboratory tests are helpful in the work-up of hepatitis A?
Liver function tests such as AST and ALT are good indicators of an HAV infection, which can exceed 10,000 mIU/mL. Bilirubin levels will also become elevated.
Where does initial infection and replication of rabies virus take place? Describe the pathway of retrograde axonal transport that allows rabies virus to enter the CNS.
Infection and replication of rabies virus occurs within striated muscle cells from initial entry via nAchRs. Eventually the virions cross across the synaptic cleft to bind to neural cell adhesion molecules (NCAMs) and enter motor and sensory neurons, which shelter rabies virus from the host immune system. Retrograde axonal transport eventually leads the rabies virus to the CNS.
What is the vaccine for rubella? What type of vaccine is it?
Live-attenuated rubella virus is available as the measles-mumps-rubella (MMR) vaccine.
A enveloped, helical, single-strand RNA virus is viewed under electron microscopy and reveals grainy particles that resemble sand. What is the most likely virus?
Viewed in cross section, arenaviruses show grainy particles that are ribosomes acquired from their host cells. The appearance resembles sand, for which their name arises (Arena is the latin root for sand).
Mutations in what two surface proteins are responsible for resistance to influenza vaccines?
HA and NA undergo antigenic variation, allowing new outbreaks resistant to previous vaccinations.
Measles strains capable of causing subacute sclerosing pan encephalitis (SSPE) lack what protein antigen?
The strains of measles virus that cause SSPE do not contain the matrix (M) protein antigen. M protein functions to regulate viral RNA synthesis and assembly. CSF taken from individuals suffering from SSPE lack antibodies to M protein.
What is the best diagnostic test for hepatitis A?
The diagnostic modality of choice for hepatitis A is serologic testing, which tests for IgM antibodies to the hepatitis A virus. Anti-HAV IgG without the presence of IgM indicates prior vaccination or past infection.
What are two of the most important causes of viral gastroenteritits worldwide?
Caliciviruses, such as norovirus, are one of the most common causes of viral gastroenteritis worldwide (in addition to rotavirus).
Asthma and RSV bronchiolitis can both present with what symptom? Why can an RSV infection occur earlier than asthma?
Asthma and RSV bronchiolitis both present with wheezing. The mechanism of asthma involves smooth muscle constriction, whereas RSV can occur in infants before smooth muscle has formed in the bronchioles.
What are the types of vaccines available for influenza? Why are they reformulated each year?
A killed virus and attenuated intranasal vaccine is available that is reformulated each year because of drifts.
Describe the prodrome and clinical presentation of rubella infection.
Incubation period is followed by a prodrome of a low-grade fever and lymphadenopathy 1 to 5 days prior to the presence of an antibody-mediated reaction of a maculopapular rash beginning on the face and spreading to the extremities.
What can blood testing reveal in a mumps infection?
Diagnosis of mumps is based on clinical features if an individual presents with parotitis. Blood testing may reveal elevated serum amylase and leukopenia with a relative lymphocytosis.
What is the pathophysiology behind the avoidance of food and water in rabies infections? What is the pathophysiology behind the mouth foaming seen in some rabies infected individuals?
Pharyngeal muscle spasms cause dysphagia, which can lead to the avoidance of food and water known as hydrophobia. Dysphagia, along with hypersalivation due to autonomic dysfunction, results in the “mouth foaming” seen in rabies encephalitis.
What is the basic virology of arenaviruses? - Enveloped/nonenveloped? - Segmented/non-segmented? - Shape? - Single/Double-stranded? - RNA/DNA?
Arenaviruses are a group of enveloped, helical, segmented, ambisense* single-stranded RNA (ssRNA).
*Arenaviruses have one negative sense and one ambisense strand of RNA.
Describe the capsid, envelope, and genetic material in a rhabdovirus.
Rabies virus has a bullet-shaped helical capsid symmetry, and is an enveloped, linear, negative sense single-stranded RNA (ssRNA) rhabdovirus.
What is the classic physical finding in the mother infected by rubella during pregnancy besides a maculopapular rash?
The common clinical presentation in pregnant women infected with rubella during the first trimester includes a maculopapular rash along with postauricular and occipital lymphadenopathy.
Describe the pathophysiology of parainfluenza once infectious aerosols are inhaled.
Infection initially occurs in the larynx mucosa via HA and NA, and eventually progresses downward to the trachea and bronchial epithelium. Inflammation and swelling of mucous membranes narrows the lumen, causing obstruction of inspiration and expiration.
How does croup appear on chest radiograph?
Diagnosis of croup is usually clinical, however chest radiograph demonstrates subglottic narrowing, commonly called the “steeple sign.”
Which RNA virus is most likely to cause chronic hepatitis?
HCV is a flavivirus that is transmitted parenterally (IV drug abuse, unprotected intercourse, needle stick, blood transfusions) and causes acute hepatitis or more commonly, a chronic carrier state. HCV infection can eventually lead to cirrhosis and hepatocellular carcinoma.
Which hepatitis viruses infect by oral-fecal transmission?
Hepatitis viruses with fecal-oral transmission include HAV and HEV. The mnemonic “vowels hit the bowels” can be used to remember these viruses.
What are two examples of Filoviruses?
Examples of filoviruses include Ebola and Marburg Virus.
What two diseases does parainfluenza cause in children?
Parainfluenza infection in children leads to croup (laryngotracheobronchitis) and pneumonia.
How is Ebola transmitted?
Transmission of Ebola occurs mainly through person-to-person contact with an infected person’s bodily fluids such as blood, vomit, urine, feces, and even sweat.
How is hepatitis C transmitted? What patient population is most at risk for infection?
Transmission primarily occurs through blood (especially transfusion and IV drug use) and less so through sexual transmission.
What cutaneous symptom raises suspicion of a Ebola virus infection?
Development of a non-pruritic maculopapular rash on the upper body during the first week of illness may be a sign of an Ebola virus infection.
When a person infected with rabies develops generalized flaccid paralysis, what is the most likely outcome?
Generalized flaccid paralysis and coma follow the acute neurologic phase, with most patients dying within 2 weeks of becoming comatose.
What are common physical exam findings in a patient with hepatitis A?
Hepatosplenomegaly, abdominal pain, and jaundice are extremely common on physical exam.
What are the initial symptoms of Ebola virus infection?
Patients typically present with an abrupt onset of fever greater than 38.6°C (101.5°F), chills, and general malaise. Other signs and symptoms can include weakness, headache, myalgia, nausea, vomiting, diarrhea, nonproductive cough, pharyngitis, and abdominal pain. Bradycardia can sometimes follow the high fever.
What virus is known as German measles?
Rubella is also known as “German measles” or the “3-day measles.”
What are the naked (nonenveloped) viruses?
Naked (i.e., nonenveloped) viruses: mnemonic “Naked Heppy (hippy) gets a CPR and PAPP smear”
- *HepE CPR** are the RNA viruses
- *PAPP** are the DNA viruses
- *Hep**atitis E
- *C**alicivirus
- *P**icornavirus
- *R**eovirus
- *P**arvovirus
- *A**denovirus
- *P**apilloma
- *P**olyoma
What is the treatment for hepatitis A?
The disease is usually self-limited and the treatment is generally supportive (i.e. hydration), as most patients (85%) recover completely within 6 months.
How is parainfluenza virus transmitted?
Transmission of parainfluenza occurs via inhalation of aerosols.
Describe the basic virology of Hepatitis C virus (capsid symmetry, enveloped/nonenveloped, and genetic material).
Hepatitis C Virus (HCV) is an enveloped, icosahedral capsid virus with a positive-sense single-stranded RNA (ssRNA) flavivirus.
What complication of measles occurs 7-10 years after the initial measles infection?
Persistent infection with a genetic variant of measles virus may lead to a fatal, progressive degenerative disease of the central nervous system known as subacute sclerosing panencephalitis (SSPE). This usually occurs 7 to 10 years after an initial measles infection. SSPE usually presents in the order listed here:
- Personality changes
- Lethargy
- Difficulty in school and odd behavior
- Progression to dementia
- Severe myoclonic jerking
- Flaccidity and decorticate rigidity
How does Ebola lead to a decrease in adaptive immunity?
Impaired dendritic function and lymphocyte apoptosis causes a decreased adaptive immunity.
A 34-year-old woman, during a visit to Nigeria, develops a fever over the course of the fifth week of her visit. The fever progresses to headache, nausea, and diarrhea. The physician is quite familiar with the symptoms in that region of Nigeria. He explains that she likely contracted her illness from rodents or from someone who had come into close contact with rodents. The woman is required to remain hospitalized because she is considered contagious. What is the most likely organism?
Lassa fever is a hemorrhagic fever restricted to West Africa. Transmission to humans occurs through aerosol spread, either from rodents or through close contact with infected individuals.
Describe how you would treat a recent rabies infection?
Tx: 1st: Wash the wound.
The rabies vaccine is a killed virus and is one of the few vaccines given after exposure to virus. Works by taking advantage of long incubation period of rabies, by increasing host immunity.
Passive immunity: Human Rabies Immune Globulin (HRIG)
What is Hepatitis E?
Hepatitis E (HEV) is a single-stranded RNA virus that is transmitted via contaminated water and the fecal-oral route. Resulting liver infection is usually self-limited.
Recently it has been put in the calcivirus family.
What are the basic virological aspects of Ebola (i.e. enveloped/non-eveloped, segmented/nonsegmented, sense, genetic material, and nucleocapsid)?
Ebola virus is a enveloped, nonsegmented, negative-sense, single-stranded RNA virus with a helical capsid. Along with Marburg virus, they make up the virus family Filoviridae, named for their thread-like filamentous structure.
Describe the basic virology of measles virus (capsid symmetry, enveloped/nonenveloped, and genetic material). What is another name for measles virus?
Measles virus (rubeola) is a helical, enveloped capsid virus with a negative single-stranded RNA (ssRNA) paramyxovirus.
What symptom is pathognomonic for measles during the prodrome phase? How does this appear on physical examination?
Koplik’s spots are pathognomonic for measles infection and appear as 1-3 mm whitish/grayish/bluish elevations with an erythematous base, typically seen on the buccal mucosa near molar teeth.
Describe the basic virology of influenza virus (capsid symmetry, enveloped/nonenveloped, segmented/nonsegmented, and genetic material).
Influenza virus is a helical, enveloped negative single-stranded RNA, segmented orthomyxovirus.
How is hantavirus transmitted?
Transmission of hantavirus occur via inhalation of aerosol of virus shed by rodent hosts (deer mouse in the US) in feces and urine.
Describe the signs and symptoms of a norwalk virus infection.
Patients with calicivirus infection present with
- Self-limiting, non-bloody diarrhea
- Nausea
- Vomiting
Describe the basic virology of parainfluenza virus (capsid symmetry, enveloped/nonenveloped, and genetic material).
Parainfluenza virus is a helical, enveloped capsid virus with a negative single-stranded RNA (ssRNA) paramyxovirus.
What preventive measures can be taken to protect against hepatitis E infection?
Preventive measures include careful cooking of food and drinking clean water.
What viruses are TORCH infections?
The infectious agents that make up “ToRCHeS” includes:
- Toxoplasmosis
- Rubella
- CMV
- Herpes Simplex and HIV
- Syphilis
What is the prodrome and common clinical manifestations of rabies?
Common manifestations of rabies include a nonspecific, flu-like prodrome (malaise, anorexia, mild fever, headache, nausea, vomiting) followed by an acute neurologic syndrome that includes
- Agitation
- Persistent fever
- Variable consciousness
- Photophobia
- Painful spasms with swallowing and/or inspiration
What is a common symptom of rubella seen in adolescent females?
Polyarthritis is common symptom seen in adolescent females.
Which virus families have segmented genomes? What does this confer?
RNA viruses can have segmented genomes. This allows alternative packaging of genetic material and the creation of new, reassorted strains with varied pathogenicity.
Viruses with segmented genomes can be remembered by the mnemonic “segmented BOAReo”
Bunyavirus
Orthomyxovirus
Arenavirus
Reovirus
Which 2 risk factors are multiplicative for hepatocellular carcinoma?
Chronic disease from HCV along with alcohol cirrhosis leads to an increased predisposition to hepatocellular carcinoma.
At what ages should children (who are able) receive the measles, mumps, rubella vaccine?
All children who are able to should receive the MMR vaccine at 12-18 months of age, with a booster given at 4-6 years.
How is hepatitis E acquired?
It most commonly occurs in fecally contaminated water sources within endemic areas and with ingestion of undercooked pork.
How is rubella virus transmitted?
Transmission of rubella occurs via aerosol droplets or transplacentally.
Describe the mode of replication once Ebola passes the point of entry into the body?
Once Ebola enters the body, the virus infects and lyses endothelial cells, hepatocytes, macrophages, and dendritic cells (antigen-presenting cells), releasing more particles into the extracellular fluid. Viral particles spread to regional lymph nodes, resulting in further rounds of replication and dissemination to other lymphoid tissues.
What do filoviruses cause?
Filoviruses cause acute hemorrhagic fever with high mortality rate.
Which hepatitis viruses are transmitted by blood, and/or are likely to cause chronic carriers, cirrhosis, and carcinoma?
Blood transmission, Chronic carriers, Cirrhosis, Carcinoma (Hep B,C, D)
What is the proposed non-primate reservoir for Ebola?
The natural reservoir for Ebola, along with the mode of transmission from reservoir to primates, remains a mystery. Bats have been suspected as being a non-primate reservoir because of their presence in areas during several outbreaks and isolation of Marburg virus from fruit bats in Uganda.
Describe the basic virology of rubella virus (capsid symmetry, enveloped/non-enveloped, segmented/non-segmented, and genetic material).
Rubella is an icosahedral, enveloped, non-segmented, positive sense single-stranded RNA (ssRNA) togavirus.
What are the best diagnostic tests for hepatitis E infection?
The best tests in diagnosing HEV infection are serum HEV RNA and anti-HEV immunoglobulin (IgM).
What are the two possible disease forms resulting from a hantavirus infection?
Two major forms of hantavirus infections include hemorrhagic fever with renal syndrome (HFRS, aka Korean hemorragic fever) and hantavirus cardiopulmonary syndrome (HCPS).
What type of antigenic variation is responsible for the seasonal flu seen in influenza?
Antigenic drifts occur every year and are due to spontaneous mutations that create slightly altered HA or NA, leading to endemic infections (seasonal flu).
Name six pathogenic flaviviruses.
The six pathogenic flaviviruses:
- Dengue fever
- Yellow fever
- Hepatitis C
- St. Louis encephalitis
- West Nile
- Japanese encephalitis
