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44 Cards in this Set
- Front
- Back
How many types of influenza are there?
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3
A,B,C |
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What type of influenza is most severe?
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Type A
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"Incubation period" for influenza
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1 - 3 days
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Potential complications of influenza
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Primary influenza pneumonia (rare)
Secondary bacterial superinfection/pneumonia (more common) |
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When is flu season?
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Late Fall, Winter, Early Spring
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What was particularly unusual about Spanish Flu Pandemic?
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Severe illness and excess mortality in healthy young adults
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How does influenza enter cells?
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Receptor-mediated endocytosis
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How many gene segments does influenza have?
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8
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What does influenza bud through?
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Host cell plasma membrane
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What 3 proteins are on influenza's surface?
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Hemagglutinin
Neuraminidase M2 |
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Characteristic of HA in infectious virions
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Has a "nick" that allows conformational change @ low pH
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Function of M2 protein
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Acts as an ion channel
Allows H+ ions into endosome Low pH allows viral RNA to separate from M1 and shell |
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Inhibiting M2 would suppress what?
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Viral replication
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Function of M1 protein
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Provides structural integrity
Underlies the lipid membrane Attached to viral RNA This attachment is compromised at low pH |
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Function of NP protein
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Covers RNA, protecting it from degradation
Contains NUCLEAR LOCALIZATION SIGNAL |
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Where does influenza replication occur?
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In the nucleus
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Function of viral transcriptase complex
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Made of PA, PB1, PB2
Initiate viral transcription in the nucleus |
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Function of NS1 protein
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Regulates splicing of mRNA
Inhibits actions of interferons made in response to infection (sequesters dsRNA) NOTE: this is NOT found in the virion Made ONLY in infected cells |
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HA recognizes this to be able to bind to cells
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Sialic acid
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What is "cap snatching"
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Influenza uses caps cleaved from 5' ends of host cell pre-mRNAs (NOT cRNA)
Caps are used to prime synthesis of viral-pre-mRNAs Caps prevent mRNA degradation |
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Where (location in cell) does HA get its "nick"?
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In the Golgi network
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What cells does influenza primarily infect?
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Ciliated epithelial cells
These cells contain protease required for HA nicking |
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Type(s) of influenza that can undergo antigenic SHIFT
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Type A only
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What is antigenic shift?
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When a type A strain is suddenly replaced by a new strain
Antigenically different HA (sometimes NA also) Shifted virus represents a new subtype |
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In what intervals are shifts observed?
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Every 10 - 40 years
Shifts are associated with pandemics |
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How many subtypes of type A influenza are there?
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At least 3
H1N1, H2N2, H3N2 |
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Why are antigenic shifts associated with severe, widespred infection?
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Population lacks neutralizing Abs
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How do antigenic shifts occur?
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When RNA segments are exchanged between viral strains in secondary host
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Type(s) of influenza that can undergo antigenic DRIFT
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BOTH types A and B
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What is antigenic drift?
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Accumulation of mutations in HA that result in inefficient Ab binding
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Where do antigenic drift mutations accumulate?
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Near the HA binding cleft for sialic acid
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NA inhibitors are effective against what types of influenza?
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BOTH types A and B
Ex. Oseltamivir |
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M2 blockers are effective against what types of influenza?
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ONLY type A
Ex. Amantadine |
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How is influenza transmitted
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As an aerosol
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This is associated with pandemics
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Antigenic SHIFT
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This is associated with epidemics
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Anitgenic DRIFT
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Why are swine good "mixing vessels"?
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Have receptors for both human and avain viruses
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Type of vaccine for influenza
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Killed
NOTE: egg-grown |
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Primary virus responsible for bronchiolitis
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Respiratory Syncytial Virus
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% of people infected with RSV by age 2
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> 95%
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Incubation period for RSV
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2-8 days
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Bronchiolitis syndrome key points
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Cough, wheeze, tachypnea, rales
Chest wall retractions CXR showing hyperinflation, atelectasis Otitis media in up to 30% of cases Peribronchiolar inflammation Epithelial necrosis |
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Bronchiolitis can cause this in immunocompromised
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Giant cell pneumonia
NOTE: this can also be caused by measles |
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Anti-viral agent used against RSV
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Ribavirin
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