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29 Cards in this Set
- Front
- Back
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What are the similarities between paramyxov and orthomyxov?
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Both are enveloped, helical and negative sense RNA viruses. Both also tend to spread via the respiratory tract.
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What is an important difference between the genome of paramyxovirus and orthomyxovirus?
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O/V have a segmented RNA genome which allows for antigenic shifts. P/V have a nonsegmented RNA genomes and most only have one serotype, allowing for long term immunity.
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Name some O/Vs and the common diseases they cause?
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Influenza A and B virus. They cause the common flu.
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Name the P/Vs and the common diseases they cause?
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Parainfluenza virus(croup, bronchitis, and bronchopneumonia), respiratory syncytial virus(RSV)(pneumonia and bronchiolitis in young infants), measles virus(measles) mumps virus(mumps).
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What is unique about the envelope of O/Vs?
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It is covered with two separate long glycoprotein spikes, hemagglutinin(HA) and neuraminidase(NA)
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What is the role of hemagglutinin in orthomyxovirus?
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HA attaches to host sialic acid on the surface of upper respiratory tract allowing for attachment of the virus. It is recognized as one of the major virulence factors associated with influenza. HA causes hemagglutinin by agglutinating RBCs via sialic acid.
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What step of O/V infection would be missing if the virus lacked HA?
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Adsorption, the virus would not be able to enter the cell.
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What is the role of neuraminidase in O/V infection?
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NA cleaves neuraminic acid and disrupts the mucin barrier. This exposes thesialic acid beneath and facilitates infection of the host cells. NA also helps release progeny virus after a cell has been infected.
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How are HA and NA attached to the viral membrane?
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They are anchored to the inside of the viral envelope by membrane proteins(M proteins).
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What do the M1 and M2 proteins do?
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M1 is a membrane protein that provides structural stability under the envelope. M2 is an ion channel that acidifies viral interior to disrupt the structure of M1 and facilitates uncoating of the virus.
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How does the drug amantadine work?
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Amantadine specifically blocks the M2 protein, thus preventing uncoating of the virus.
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Describe the internal structure of an orthomyxovirus.
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Helical capsid with 8 segmented single stranded negative sense RNA genome.
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What is unique about influenza genome replication?
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Only other RNA virus, besides retroviruses, that has genome synthesis inside the nucleus.
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How many types of the influenza virus are there?
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Three. A, B< and C
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Does the influenza virus infect other organisms besides humans?
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Yes. Influenza A is able to infect mammels and birds in addition to humans. Influenza B and C can only infect humans.
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In 1918, app. 20 million people worldwide died from the influenza virus. What is this an example of?
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A pandemic(worldwide)
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Which strains of influenza are involved with pandemics?
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Only influenza A. It is the only starin that infects animals other than humans. This allows for antigenic shift. Influenza B is known to cause outbreaks, while influenza C typically causes mild infections.
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Whatn is the difference between antigenic shift and antigenic drift?
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Antigenic shift involves the creation of entirely new starins of influenza based on the exchange of genomic segments between human srains and animal strains. Antigenic drift involves minor mutations in HA or NA that changes the antigenic nature of these glycoproteins.
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Why are new versions of the influenza vaccine introduced every year?
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Antigenic drift
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Who is most likely to suffer serious complications from influenza?
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Elderly and immunocompromised hosts
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How can infection with influenza contribute to bacterial pneumonia?
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The viral infection lowers the host defenses against many bacteria, most notably Staph. aureus and Strep. pneumoniae.
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What are thesymptoms of Reye's syndrome?
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Coma, fatty liver and encephalopathy
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What is the cause of Reye's syndrome?
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There is evidence that salicylate use in children with influenza and chickenpox may cause this serious condition. Salicylates should never be given to children to reduce fevers.
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What's another medical complication that can arise from influenza infection?
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Guillain-Barre' syndrome
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What laboratory tests could be used to confirm an influenza infection?
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Culture(viral isolation) detection of viral proteins, detetion of viral RNA andserological tests.
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What drugs are available to treat influenza/
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Amantadine/Rimantidine which work by preventing viral uncoating or zanamivir(inhaled)/oseltamivir(Tamiflu,oral which areNA inhibitors.
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Should Amantidine/rimantidine be given to patients with active symptoms of the flu?
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Yes, amantidine has been shown to reduce the duration of illness in adults if given within 48 hrs of onset of symptoms. Amantidine can also be used prophylactically in adults and children. However, it is only effective against influenza A.
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What medicine can be used against influenza B?
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Zanamivir and oseltamivir can be used against both A and B types. They have been shown to be effective in reducing the duration of symptoms and preventing infection.
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What is the best way to prevent influenza infection?
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Vaccine. Typically contains 2 killed strains of influenza A and 1 strain of B.
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