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135 Cards in this Set
- Front
- Back
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What is single-stranded RNA?
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RNA that has 1 strand of nucleic acid
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What is unique about negative ssRNA?
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Negative ssRNA must first be converted into positive ssRNA before it can be translated.
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What enzyme is needed to aid in te replication of -ssRNA?
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RNA-dependent RNA polymerase
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What is the general site of nucleic acid replication of RNA viruses?
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Cytoplasm
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What RNA viruses are the exceptions?
Where do they replicate? |
Orthomyxoviridae (-ssRNA)
Retrovirus (+ssRNA) Nucleus |
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What is an enveloped virus?
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A virus that has a lipid bilayer outer membrane surrounding its nucleic acid, which when present, plays an important role in viral penetration.
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How do viruses acquire this envelope?
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From host cell membrane 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 are capsids?
What do they look like? |
Proteinaceous shells that surround viruses.
Icosahedral Helical |
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What are the enveloped -ssRNA virus families?
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1) Filoviridae
2) Orthomyxoviridae 3) Bunyaviridae 4) Arenaviridae 5) Rhabdoviridae 6) Paramyxoviridae |
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What's the capsid geometry of -ssRNA viruses?
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Helical
All -ssRNA have: Envelopes Helical capsids |
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What are the arthropod borne viruses?
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Flaviviridae (-ssRNA)
Bunyaviridae (-ssRNA) Togaviridae (+ssRNA) |
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What is a segmented genome?
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A genome that is physically separated into several segments.
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What viruses have segmented genomes?
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Bunyavirus (-ssRNA)
Orthomyxovirus (-ssRNA) Arenavirus (-ssRNA) Reovirus (dsRNA) BOAR |
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What type of nucleic acid do Bynyaviridae contain in their genome?
What's their capsid geometry? Do they contain an envelope? |
-ssRNA with a three-part segmented genome
Helical YES |
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What four genera are associated with Bunyaviridae?
Which are arthropod borne? |
Hantavirus
Bunyavirus Phlebovirus Nairovirus All except hantavirus |
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What are two species of Hantavirus?
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Sin Nombre
Hemorrhagic fever with renal syndrome (Korean fever) |
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What is the reservoir for Hantavirus?
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Deer mouse
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Where in the US is hantavirus endemic?
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SW States
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How is hantavirus transmitted?
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Aerosolized rodent excretions
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What are the mild clinical manifestations of hantavirus?
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Influenza-like illness
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What are the severe clinical manifestations of hantavirus?
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Hemorrhagic fever, acute renal failure, adn a pulmonary cyndrome with a high mortality.
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What is the mortality of hantavirus pulmonary syndrome?
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80%
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What are two species of bunyavirus?
What do they cause? |
California Encephalitis
La Crosse Encephalitis |
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What is the reservoir for California encephalitis?
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Rodents and rabbits
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How is the bunyavirus acquired?
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Animal bites
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How does the bunyavirus reach the brain?
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Hematogenously secondary to viral replication at entry point.
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What time of year does bunyavirus comonly affect humans?
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Summer
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How common is death from bunyavirus?
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Rare
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What are two species of Phlebovirus?
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Rift Valley fever
Sandfly fever |
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What organisms are usually affcted by Rift Valley fever?
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Domesticated animals
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What name is given to this form of infection (Phlebovirus infecting domesticated animals)?
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A zoonosis, e.e., a disease that predominantly affect animals.
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How is the Phlebovirus transmitted?
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Via mosquitos, e.g., Aedes spp. that have fed on infected livestock.
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What is the most common complication of Rift Valley fever?
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Retinitis
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How common is death due to Rift Valley fever?
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Death is rare
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What are the clinical manifestations of sandfly fever?
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Sudden onset of fever,
Frontal headache, Low back pain, Retro-orbital pain Malaise |
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What is a species of Nairovirus?
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Crimean Congo hemorrhagic fever
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How is Nairovirus transmitted?
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Ticks
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What are the symptoms of nairovirus?
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Initial fever
Myalgia Vertigo Photophobia Vomiting followed by Mental status changes |
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What type of nucleic acid do Orthomyxoviridae contain in their genome?
What is their capsid geometry? Do they contain an envelope? |
-ssRNA with an eight-part segmented genome.
Helical YES |
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What disease is caused by Orthomyxoviridae?
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Influenza
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what is teh incubation period of influenza caused by Orthomyxoviridae?
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24-48 hours
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What are the clinical manifestations of influenza caused by Orthomyxoviridae
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Sudden onset of symptoms, i.e.,
Fever, Myalgia, Headache, Cough, and Fatigue |
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What are three important glycoproteins associated with influenza virus?
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Hemagglutinin (HA)
Neuraminidase (NA) M2 |
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How does hemagglutinin contribute to pathogenesis?
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Promotes viral entry into the cell by acting as the viral receptor resulting in viral-cell fusion.
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How does hemagglutinin promote viral-cell fusion?
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Attaches to sialic acid receptors on host cell
Creates conformational changes at low pH inside the host cell endosome |
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How does neuraminidase contribute to pathogenesis of Orthomyxoviridae?
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1) Prevents binding of virus back to infected cells by cleaving host cel sialic (neuraminic) acid, allowing progeny virus to infect uninfected cells and not be 'wasted' on previously infected cells.
2) Disrupts the mucin of healthy mucosal epithelial cells, exposing new sialic acid binding sites for virions |
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How does M2 contribute to pathogenesis of Orthomyxoviridae?
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Acts as an ion channel within the endosome allowing H+ to enter the virion and viral RNA to be released to the cytoplasm.
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What are the treatment implications of understanding the glycoprotiens associated with Orthomyxoviridae?
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HA, NA, adn M2 protein are cellular targets used to suppress influenza infections.
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What is different about influenza replication when compared to the majority of other RNA viruses?
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Replication occurs in the nucleus Orthomyxoviridae and Retroviridae (+ssRNA) are the only RNA viruses that replicate in the nucleus.
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What is one defense mechanism of influenza virus?
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Suppressing the host cell antiviral mechanism with viral NS1 protein preventing PKR activation.
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How does PKR work?
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PKR activation temporarily halts host cell protein synthesis, preventing viral used of host machinery and decreasing viral protein synthesis.
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What does teh body use to combat the destruction of respiratory epithelial cells influenza virus?
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Cytotoxic CD 8+ T cells
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What are three strains of influenza viruses?
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A
B C |
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Which strain causes worldwide flu pandemics at intervals of 10-20 years?
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Influenza A
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Which strain causes major seasonal outbreaks of influenza?
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Influenza B
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Which strain is associated with mild respiratory tract infections?
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Influenza C
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What is the distinguishing feature between influenza A, B, and C?
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Each has different internal proteins, mainly matrix proteins (M) and nucleocapsid proteins (NP).
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Which viruses are associated with Reye syndrome and liver degeneration?
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Influenza B
Varicella |
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Which drug is associated with Reye syndrome?
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Aspirin use in pediatric patients
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What is Reye syndrome?
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Noninflammatory encephalopathy with hepatic failure.
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What is the best site on the influenza virus to target an immune response?
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Antibodies against the HA glycoprotein
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What are two important changes occurring in influenza virus resulting in genetic diversity?
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Antigenic shift
Antigenic drift |
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What is antigenic shift?
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Major antigenic changes characterized by sudden replacement of a new strain with an antigenically different HA and NA occcurring by reassortment of viral RNA segments (HA1NA1 to HA3NA2)
Antigenic shift only occurs in type A |
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How often does antigenic shift occur?
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Every 10-40 years.
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What is antigenic drift?
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Minor antigenic changes characterized by random point muttions in viral RNA leading to amino acid substitutions in HA glycoproteins.
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Which strains demonstrate antigenic drift?
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Influenza A and B
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How often does antigenic drift occur?
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Every 2-3 years
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Which two drugs are effective against both influenza A and B?
What is the mechanism of action? |
Zanamivir
Oseltamivir Inhibit NA |
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Which two drugs are only effective against influenza A?
What is the mechanism of action? |
Amantadine
Rimantadine Blocks viral uncoating by inhibition of influenza viral M2 membrane protein. |
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What immunoglobulin mediates immunity against influenza virus?
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Secretory IgA in respiratory tract
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What are Paramyxoviridae?
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Enveloped, helical negative ssRNA virus.
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What four genera are in the Paramyxoviridae family?
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Paramyxoviridae
Rubulavirus Morbillivirus Pneumovirinae |
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What are four clinical manifestations caused by Paramyxoviridae infections?
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Parainfluenza/croup (Paramyxoviridae)
RSV (Pneumovirinae Mumps (Rubulavirus) Measles (Morbillivirus) |
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Which Paramyxoviridae membrane lycoprotein is responsible for viral-cell fusion?
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F protein
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What is another name for croup?
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Actue laryngotracheobronchitis
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Do Paramyxoviridae have HA and NA?
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YES
Both are present |
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How is it possible to distinguish beetween influenza and parainfluenza in regards to HA and NA?
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In parainfluenza, HA and NA are on the same surface spikes
In influenza, HA and NA are on different surface spikes. |
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What are the clinical characteristics of parainfluenza?
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Upper and lower respiratory tract infection without viremia.
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In what patient population is respiratory syncytial virus responsible for bronchiolitis?
What is this? |
Palivizumab (Synagis)
A monoclonal antibody to RSV |
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What is the clinical presentation of mumps?
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Swollen parotid glands
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What are three possible postinfection sequelae of mumps?
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Parotitis
Orchitis Aseptic meningitis |
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When is the yearly peak incidence of mumps?
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Winter
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Are HA and NA present in mumps?
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YES
Both are present |
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What is the cell receptor for measles?
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CD46 molecule
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How are measles transmitted?
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Respiratory droplets
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What are the clinical features of measles?
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1) Prodromal period of fever
2) Upper respiratory symptoms 3) Maculopapular rash 4) Koplik spots 5) Conjunctivitis |
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How does the maculopapular rash associated with measles spread?
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Cranial caudally, i.e., away from the head
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What are Koplik spots?
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White spots on brignt-red oral mucous membranes.
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What is the characteristic cytopathoogy of measles?
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Multinucleated giant cells due to fusion of F proteins
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What is a severe complication of measles several years following infection?
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Subacute sclerosing panencephalitis
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Are HA and NA present in measles?
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Only HA is present
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What are Rhabdoviridae?
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Enveloped, helical, -ssRNA, bullet-shaped viruses.
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What genera are in the Flaviviridae family?
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Lyssavirus
Vesiculovirus |
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What major human pathogen is in the Rhabdoviridae family?
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Rabies virus (Lyssavirus)
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What is the structure of the rabies virus?
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Bullet-shaped capsid with an antigenic G-glycoprotein on envelope.
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What is the cell receptor for rabies?
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Acetylcholine receptor
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How does the rabies virus infection spread within the nervous system?
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Retrograde axoplasmic transport from peripheraal neurons to the central nervous system (CNS)
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How long is the incubation period for rabies?
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2 weeks to 1 year
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What symptoms are associated with rabies?
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Painful spasm of throat muscles upon swallowing and hydrophobia.
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What histologic finding is associated with rabies?
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Negri bodies
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What do Negri bodies look like?
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Eosinophilic cytoplasmic inclusion bodies.
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How is rabies infection prevented in individuals at high risk of exposure?
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Avoidane of rabid animals
Preexposure prophylactic immunization with human diploid cell vaccine (HDCV) |
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What is the treatment for rabies infection?
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Postexposure immunization with HDCV and rabies virus Ig.
Rabies virus vaccine and Hepatitis B virus vaccine are the only vaccines that can be given effectively postexposure. |
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What is the cause of death once rabies symptoms become evident?
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Respiratory center dysfunction and encephalitis.
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What is Vesiculovirus?
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The best studied Rhabdoviridae, Vesiculovirus infects cattle and horse, causing vesicular stomatitis, but does not cause disease in humans.
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What is Filoviridae?
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Enveloped, helical, -ssRNA viruses
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What are two Filoviridae that are human pathogens?
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Marburg virus
Ebola virus |
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What are the clinical manifestations of Filoviridae infections?
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Severe hemorrhagic fever with widespread bleeding from skin, mucous membranes, and visceral organs
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What is the mechanism for hemorrhagic fever?
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Virus contains proteins that mimic factors inducing the coagulation cascade, leading to the depletion of clotting factors.
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What animal was the original source for Marburg virus?
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African green monkey
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What is the route of transmission for Marburg?
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Airborne transmission and blood exposure.
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What is the incubation period for Marburg?
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7-21 days
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What is the clinical presentation of Marburg?
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Muscle aches, mild fever, nausea, vomiting, rash, and bloodshot eyes with defacation of blood approximately 10 days later
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What is the mortality rate of Marburg?
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25%
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What is the mode of transmission for Ebola virus?
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Direct contact with body fluids
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What component of the Ebola virus is responsible for its cytotoxic effects?
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Modified glycoprotein on the virus
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What cells are most susceptible to these cytotoxic effects?
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Endothelial cells
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How was the Ebola virus initially isolated?
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From patients with hemorrhagic fever in Zaire and Sudan.
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What are the clinical manifestations fo Ebola virus?
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Fever, diarrhea, weakness, and bleeding from mucous membranes
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What is the mortality rate of Ebola?
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65%
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What are arenaviridae?
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Enveloped, helical, -ssRNA viruses
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What animal is associated with Arenaviridae?
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Rodents
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How is the virus transmitted?
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Inhaling aerosolized virus particles or eating contaminated food.
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What are two diseases caused by Arenaviridae?
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Lymphocytic choriomeningitis
Lassa fever |
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What are the clinical manifestations of Lymphocytic choriomeningitis?
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Influenza-like illness sometimes associated with a viral meningitis that has a relatively benign course and low mortality.
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What are the clinical manifestations of Lassa fever?
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Hemorrhagic fever with nausea, vomiting, severely bloodshot eyes, and a painful rash after rodent exposure
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What is the mortality rate of Lassa virus?
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50%
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What is the only virus found in the Deltaviridae genus?
What type of virus is it? |
HDV
A defective RNA virus |
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What causes detrimental HDV infections?
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Liver cells already inhabited by the hepatitis B virus, a dsDNA virus
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How does HDV replcicate?
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Using a HBV reverse transcriptase
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What makes HDV dependent on HBV?
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1) HDV uses HBV-encoded reverse transcriptase
2) HDV requires the protective HBV envelope |
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What are three types of HDV and where do they exist?
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Type I, which exists in North America and Italy
Type II, which exists in Japan and Taiwan Type III, which exists in South America |
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What is the clinical consequence of HDV superinfection in HBV-infected individuals?
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The superinfection causes a more aggressive form of hepatitis.
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How can one avoid detrimental HDV infection?
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HBV vaccination?
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