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.