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133 Cards in this Set
- Front
- Back
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What is single-stranded RNA?
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Ribonucleic acid that has 1 strand of nucleic acid.
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What are two classifications of ssRNA?
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Positive ssRNA
Negative ssRNA |
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What is positive ssRNA
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Positive ssRNA is a form fo RNA which can be translated into proteins using host cell machinery, thus being directly infectious
Similar to mRNA |
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What is negative ssRNA?
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Negative ssRNA must first be used as a template for positive strand synthesis.
The positive strand is then translated into proteins or used as a template to synthesize progeny genomic RNA. |
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What enzymes do positive ssRNA need for replication?
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Virus-encoded RNA-dependent RNA polymerases
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What is the general site of nucleic acid replication of RNA viruses?
What RNA viruses are the exceptions? Where do they replicate? |
Cytoplasm
1) Retrovirus (+ssRNA) 2) Orthomyxoviridae (-ssRNA) Nucleus |
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What is an enveloped virus?
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A virus which has a lipid bilayer outer membrane surrounding its nucleic acid which plays an important role in viral penetration.
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Where do viruses acquire this envelope?
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From host cell membranes secondary to viral host cell budding.
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How do enveloped viruses enter host cells?
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Fusion of the viral envelope with the host cell membrane.
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What is a nonenveloped virus?
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A virus without an outer membrane
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What are two mechanisms by which nonenveloped viruses enter host cells?
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1) Injection of nucleic acid through the cytoplasmic membrane of host cells.
2) Receptor-mediated endocytosis of the virus. |
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What are capsids
What are two conformatoins that they assume? |
Proteinaceous shells that surround viruses
Icosahedral Helical |
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What are the three nonenveloped positive ssRNA families?
What is their capsid geometry? |
Picornaviridae
Caliciviridae Astroviridae Icosahedral |
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What are the four enveloped positive ssRNA virus families and capsid geometry?
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1) Coronaviridae, helical
2) Togaviridae, icosahedral 3) Flaviviridae, icosahedral 4) Retroviridae, complex |
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What are the arthropod borne viruses?
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Flaviviridae (+ssRNA)
Togaviridae (-ssRNA) Bunyaviridae (-ssRNA) |
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What viral RNA genomes are translated immediately by host cell machinery upon entry into a cell and are analogous to mRNA?
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Positive-strand RNA
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What type of nucleic acid do Picornaviridae contain in their genome?
What is their capsid geometry? Do they contain an envelope? |
Positive ssRNA
Picornaviridae has teh smallest RNA genome Icosahedral NO |
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What are five genera of Picornaviridae?
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Polio
Echovirus Rhinovirus Coxsackievirus Hepatitis A virus PERCH |
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What are enteroviruses?
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Viruses that affect the GI tract.
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Which picornaviruses are enteroviruses?
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Polio
Echovirus Coxsackievirus HAV Enteroviruses are a major causes of CNS disease, especially acute aseptic meningitis. |
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How does the poliovirus attach to cells?
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Via the polio virus receptor (PVR).
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What is the poliovirus' defense mechanism?
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Proteolytic degradation of PKR
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What is PKR?
What's it's function? |
An RNA-activated protein kinase
PKR activation temporarily halts host cell protein synthesis, preventing viral use of host machinery and decreasing viral protein synthesis. |
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Which cells does the poliovirus target?
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Peyer patch
Motor neurons |
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What are three clinical outcomes of infection with poliovirus?
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No illness (95%)
Minor illness (4%) Major illness (1%) |
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What are the clinical manifestations of a minor illness of poliovirus?
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Nonspecific symptoms of headache, sore throat, and nausea.
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Waht are two clinical manifestations of the major illness?
What are the characteristics? |
1) Nonparylytic polio is characterized headache, muscular spasm, nausea, and abdominal pain, lethary, and irritability; often indistinguishable form aseptic meningitis.
2) Paralytic polio is usually characterized by asymmetric proximal paralysis of the lower/upper limbs, abdomen, and sometimes can spread cranially causing respiratory paralysis |
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How does the poliovirus replicate and ultimately penetrate the CNS?
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1) Viral replication in tonsils and Peyer patches
2) hematogenous spread allowing virus exposure to teh blood-brain barrier 3) Attachment and penetration of anterior horn motor neurons of the spinal cord. |
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How si poliovirus transmitted?
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Fecal-oral transmission
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What are the two forms of polio vaccines?
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1) Salk: killed poliovirus vaccine
2) Sabin: live-attenuated poliovirus |
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What type of Ig is produced in response to both vaccines?
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IgG
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What type of immunoglubulin is initially induced by the Sabin vaccine but not by the Salk vaccine?
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Intestinal IgA
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What is the risk of the Sabin vaccine that is not seen with the Salk vaccine?
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Reversion to a virulent form.
The attenuated vaccine's genome is only 2 point mutations different form the wild-type virus. Killed vaccines cannot revert to a more virulent form and cause disease |
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What is an advantage of the Sabin vaccine?
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Induces herd immunity
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What four clinical features are common to coxsackievirus viruses and echoviruses?
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1) Mild febrile infections
2) Respiratory infections 3) Rashes 4) Aseptic meningitis |
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What are two pathogenic coxsackievirus viruses?
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1) Coxsackievirus virus A
2) Coxsackievirus virus B |
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What are three clinical manifestations of coxsackievirus virus A?
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1) Herpangina
2) Hand-foot-and-mouth disease 3) Acute hemorrhagic conjunctivitis |
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What is herpangina?
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Disease entity characterized by fever and sore throat with red vesicles on back of throat.
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What is hand-foot-and-mouth disease?
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Disease entity characterized by vesicular eruptions restricted to the hands and feet and in the mouth; generally seen in children.
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What are three clinical manifestations of coxsackievirus virus B?
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Myocarditis
Pericarditis Pleurodynia |
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What is pleurodynia?
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Disease entity characterized by pleuritic pain upon breathing, fever, and headache, which is life-threatening for infants.
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What are other names for pleurodynia?
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Bornholm disease, epidemic myalgia, and "devil's grip".
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What does 'Echo' stand for?
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Enteric cytopathic human orphan
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What diseases do echoviruses cause?
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Echoviruses rarely cause disease
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What are four rare clinical manifestations of echovirus?
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1) Viral meningitis
2) Pericarditis 3) RAshes 4) Cold-like symptoms |
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How many serotypes of HAV exist?
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1
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How is HAV transmitted?
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Fecal-oral transmission, commonly from eating uncooked shellfish harvested from sewage-contaminated water.
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What other hepatitis virus is transmitted fecal-orally?
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Hepatitis E virus
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Does HAV predispose one to hepatocellular carcinoma?
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NO
Hepatitis A and E viruses are not linked to hepatocellular carcinoma. |
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What is the overall death rate from HAV infection?
What patient population is at highest risk for death? |
<1%
Pregnant women |
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What is teh typical incubation period after exposure to HAV?
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15-40 days
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What are three clinical manifestations of HAV?
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1) Painful hepatomegaly
2) Jaundice 3) Fever |
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What is the treatment for HAV?
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Patients with HAV infection should receive pooled immunoglobulin and supportive treatment
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Is there a vaccine for HAV?
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YES
An inactivated viral vaccine is administered in two doses to those at risk. |
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What does rhinovirus cause?
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common colds
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What makes rhinovirus different from other enteroviruses?
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1) Replicate in cooler body temperatures such as found in the nose.
2) Rhinoviruses are acid labile Rhino=common cold in cooler areas. |
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What is the usual treatment for a rhinovirus infection?
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Supportive care
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What group of drugs is often incorrectly prescribed to patients with a common viral cold?
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Antibiotics
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What typeof nucleic acid do Calciviridae contain in their genome?
What is their capsid geometry? Do the contain an envelop? |
+ssRNA
Icosahedral NO |
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What viruses are the calciviridae family?
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Norwalk virus
Hepatitis E virus |
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What are clinical manifestations of Norwalk virus infection?
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Gastroenteritis with explosive diarrhea without blood or pus, in addition to fever, vomiting, and abdominal pain.
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How is Norwalk virus transmitted?
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Fecal-orally
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which patient population is affected by acute epidemic gastroenteritis from Norwalk virus?
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Adult in close quarters, e.g., military bases, retirement communities, and cruise ships, and school-age children.
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What is the disease course of the Norwalk virus?
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24-48 hours of self-limited symptoms
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What causes death in patients with Norwalk virus?
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Dehydration and electrolyte losses
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What is the treatment for Norwalk virus infection?
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Supportive treatment including fluid replacement.
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What are the clinical manifestations of HEV?
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Similar to HAV
1) Painful hepatomegaly 2) Jaundice 3) Fever Although HEV and HAV have similar clinical manifestations, they are two genetically distinct viruses. |
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How is HEV transmitted?
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Fecal-orally
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Does HEV predispose one to hepatocellular carcinoma?
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NO
Hepatitis E and A viruses are not linked to hepatocellular carcinoma. |
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What patient population is HEV infection especially severe?
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Pregnant women
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Where is HEV responsible for epidemic outbreaks of hepatitis?
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Asia
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What is the treatment for HEV?
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Supportive treatment
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Is there a vaccine for HEV?
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NO
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What type of nucleic acid do Coronaviridae contain in their genome?
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Helical
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Do Coronaviridae contain an envelope?
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YES
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What does Coronaviridae cause?
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Common colds
SARS |
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What type of nucleic acid do Togaviridae contain in their genome?
What is their capsid geometry? do they contain an envelope? |
+ssRNA
Icosahedral YES |
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What genera are in the Togaviridae family?
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Alphaviridae
Rubivirus |
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How are alphaviruses transmitted?
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Mosquitos transmit to humans and domestic animals.
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What name is given to viruses that are transmitted via mosquito?
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Arboviruses
ARthropod BOrne viruses |
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What are four viruses in the alphaviridae?
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1) Eastern equine encephalitis viruses
2) Western equine encephalitis viruses 3) Chikungunya viruses 4) Venezuelan equine encephalitis viruses |
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What are three clinical manifestations of Alphaviridae?
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1) Eastern/Western equine encephalitis viruses-acute encephalitis
2) Chikungunya viruses-acute arthropathy 3) Venezuelan equine encephalitis viruses - febrile illness with flu-like symptoms |
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What virus belongs to the Rubiviridae genus?
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Rubella virus (German measles)
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What are the clinical features of rubella?
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General maculopapular rash beginning on the face and progressing to extremities, along with posterior auricular occipital lymphadenopathy
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How is rubella most commonly transmitted?
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Respiratory droplets
Transplacentally |
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What are the clinical complications of rubella infection during pregnancy?
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Teratogenic effects on teh developing fetal CNS, liver, heart, and eye in the first trimester of pregnancy.
Tubella is the "r" in TORCHEs, i.e., the mneumonic given to remember common congenital infections: Toxoplasmosis Other (HIV) Rubella Cytomegalovirus Herpes Syphilis |
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What are the CNS complications of congenital rubella?
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Deafness
Microencephaly Mental Retardation |
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What are the heart complications of congenital rubella?
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Patent ductus
Interventricular septal defects Pulmonary artery stenosis |
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What are the eye complications of congenital rubella?
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Cataracts and chorioretinitis
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When are these complications most severe?
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When rubella infection occurs during the first trimester
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What type of nucleic acid do Flaviviridae contain in their genome?
What is their capsid geometry Do they contain an envelope? |
+ssRNA
Icosahedral YES |
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What genera are in teh Flaviviridae family?
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Flavivirus
Hepatitis C virus |
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What six diseases are associated with flavivirus?
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1) Yellow fever
2) Dengue fever 3) HCV 4) West Nile Fever 5) St. Louis encephalitis 6) Japanese encephalitis |
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What is the historical significance of yellow fever?
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First human virus discovered
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What is the vector for yellow fever?
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Aedes aegypti mosquito
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What is the clinical presentation of Yellow fever?
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Hepatitis, jaundice, fever, backache, and blackvomitus 1 week postmosquito bite.
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What histologic finding is seen in liver specimens following yellow fever infection?
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Councilman bodies
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What do councilman bodies look like?
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Acidophilic inclusions
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Is there a vaccine for yellow fever?
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YES
Live-attenuated vaccine |
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What is another name for dengue fever?
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Break-bone fever
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What is the vector for Dengue fever?
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Aedes aegypti mosquito
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How many serotypes of Dengue virus exist?
What si the significance of this? |
Four
Dengue hemorrhagic fever results from an infection with a serotype different from a first infection. |
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What are the clinical manifestations of dengue fever?
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Hemorrhagic fever and shock syndrome, with painful crisis, including backache, headache, muscle and joint pain.
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What is hemorrhagic fever?
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High fever and increased vascular permeability.
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What is hemorrhagic shock syndrome?
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A complication of dengue hemorrhagic fever with signs of circulatory failure.
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What are four warning signs of hemorrhagic shock syndrome?
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1) Constant abdominal pain
2) Restlessness alternating with lethargy 3) Persistent vomiting 4) Change from fever to hypothermia. |
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What causes the symptoms?
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The immune response to teh virus, including increased vascular permeability and disseminated intravascular coagulation caused by circulating dengue antigen-antibody complexes and complement activation.
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What predisposes one to a more virulent form of dengue fever?
What causes this? |
Previous episode with dengue fever.
Because of the presence of memory cells to viral antigens there is a faster immune response than the initial response Although this is expected, thefaster inflammatory response causes a more severe form of the disease |
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What are three modes of HCV transmission?
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Blood
Birth Sex |
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What are two scenarios in which HCV is likely to have been transmitted by blood?
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Posttransfusion hepatitis
Patient on hemodialysis with hepatitis |
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What is the increased risk factor for HCV infection?
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Hepatocellular carcinoma
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What percentage of those infected with HCV develop...
Chronic hepatitis? Cirrhosis? |
50%
20% |
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What is the treatment for HCV?
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Interferon-alpha
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What is the success rate of interferon-alpha treatment for HCV?
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Significantly increased the risk of hepatocellular cancer.
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Is there a vaccine for HCV?
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NO
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What is the number one etiology for chronic hepatitis in the US?
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HCV
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What is the number one etiology for chronic hepatitis worldwide?
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HBV
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How is West Nile fever spread?
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Mosquitoes
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What is the reservoir for West Nile Fever?
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Birds
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How does West Nile fever present clinically?
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Rash
Lymphadenopathy Fever Malaise |
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What is the prognosis of West Nile fever?
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Most people recover, but the elderly are more likely to develop meningitis or encephalitis which may be fatal.
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Where is St. Louis encephalitis endemic?
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Ohio, Gulf coasts and western states
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What is the vector for St. Louis encephalitis?
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Culex spp. mosquitos
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Where is Japanese encephalitis endemic?
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Mainly China, very little in Japan
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What is the vector for Japanese encephalitis?
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Culex spp. mosquitos
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What are Retroviridae?
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Enveloped +ssRNA with a complex capsid.
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What enzyme is unique to Retroviridae?
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Reverse transcriptase
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What's the function of reverse transcriptase?
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Produces a dsDNA intermediate during the replication of the +ssRNA genome.
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What are three genera of Retroviridae?
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Lentivirus
Oncomavirus Spumavirus |
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What are three general components of the retrovirus structure?
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1) Lipid mebrane envelope (host-cell derived)
2) Complex capsid 3) Nucleoprotein |
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What are three envelope proteins associated with the lipid envelope?
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1) Transmembrane glycoprotein (TM, fusion protein and gp41)
2) Surface glycoprotein (SU, attachment protein, and gp120) 3) Outer matrix protein (MA, and p17) |
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What is an important protein of the capsid?
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Major capsid protein (p24)
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What are three components of the nucleoprotein?
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p7
+ssRNA Reverse transcriptase |
