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11 Cards in this Set
- Front
- Back
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A touch of the flu: site of infection, congestion, cough, fever, onset, myalgia prostration and malaise, acute illness, secondary bacterial pneumonia, epidemiology
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Site: Upper RT
Congestion: Pronounced Cough: Productive Fever: Little if any Onset: Gradual Myalgia, prostration, malaise: Rare Acute Illness: 1 day Secondary bacterial pneumonia: rare Epidemiology: Sporadic |
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Influenza: site of infection, congestion, cough, fever, onset, myalgia prostration and malaise, acute illness, secondary bacterial pneumonia, epidemiology
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Site: Middle RT
Congestion: Mild Cough: Dry Fever: High Onset: Sudden Myalgia, prostration, malaise: Pronounced Acute Illness: 3 days Secondary bacterial pneumonia: Frequent Epidemiology: Epidemic |
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Negative strand RNA virus classification
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Segmented: Orthomyxoviruses
-Influenza All enveloped: Paramyxoviruses -RSV -Parainfluenza |
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Structure of Influenza Viruses
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Enveloped
Helical nucleocapsids contain 8 different segments of RNA that constitute genome -encode 10 different proteins -hemagglutinin and neuraminidase (spike like proteins) -M2 - ion channel (target) -M1 Matrix protein -RNA polymerase |
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Virus replication cycle
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Attachment:
1. Viral attachment protein: hemagglutinin 2. Cellular receptors: sialic acid Penetration: 1. Endocytosis followed by envelope fusion with endosome membrane Uncoating: 1. Dissociation of matrix (requires M2 ion channel, site of action of amantadine) 2. Transport of nucleocapsid to nucleus Gene expression and genome regulation: 1. Synthesis of mRNAs and proteins 2. Splicing of M2 and NS2 mRNAs 3. Replication of genome Assembly and release: 1. Assembly of nucleocapsids in the nucleus 2. Transport to the cytoplasm (requires NS2) 3. Budding from host membranes (reassortment) 4. Neuraminidase causes release from cell receptors (site of action for zanamivir et al.) |
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Types and Subtypes of Influenza Viruses
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Most cases due to Type A, smaller portion due to Type B, Type C not cause of epidemic
Type A Subtypes: 3 Hemagluttinin subtypes affect humans (15 in total), H1, H2, H3 2 Neuraminidase subtypes affect humans, N1 and N2 Usually see H1N1, H2N2, H3N2 Antigenic drift doesn't change subtype, antigenic shift does |
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Current Influenza Vaccines
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Two formulations
-Inactivated (“killed virus”) -Live, attenuated (nasal spray) Both formulations have 3 strains: -Influenza A (H1N1) virus -Influenza A (H3N2) virus -Influenza B virus About 70-80% protection |
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Influenza Antiviral Drugs
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Ion channel (M2) blockers
-Amantadine (Symmetrel) -Rimantidine (Flumadine) -most current strains are resistant to these drugs Neuraminidase (NA) inhibitors -Zanamivir (Relenza) -Oseltamivir (Tamiflu) |
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Respiratory Disease Syndromes Caused by Respiratory Syncytial and Parainfluenza Viruses
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Upper respiratory infection: most common outcome in adults
Croup (laryngo-tracheo-bronchitis): Only occurs in infants; parainfluenza more common than RSV Bronchitis/bronchiolitis: Occurs in infants, children, and the elderly; RSV more common than parainfluenza Viral pneumonia: Occurs in infants, children, and the elderly; RSV more common than parainfluenza |
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Major Differences Between Influenza Viruses
And Parainfluenza/RSV (Clinical) |
Upper RT infection: Influenza=common, Parainfluenza/RSV=common
Viral pneumonia: influenza=rare, Parainfluenza/RSV=common Secondary bacterial pneumonia: influenza=common, Parainfluenza/RSV=rare Vaccine: influenza=yes, Parainfluenza/RSV=no Antivirals: influenza=yes, Parainfluenza/RSV=no |
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Major Differences Between Influenza Viruses
And Parainfluenza/RSV (Basic) |
Attachment protein: Influenza=HA, Parainfluenza/RSV=HN (RSV-G)
Fusion protein: Influenza=HA, Parainfluenza/RSV=F Release protein: Influenza=NA, Parainfluenza/RSV=HN (RSV-?) Site of envelope fusion: Influenza=Endosome, Parainfluenza/RSV=Plasma membrane Site of replication: Influenza=nucleus, Parainfluenza/RSV=cytoplasm Produces spliced mRNA: Influenza=yes, Parainfluenza/RSV=no Genome: Influenza=segmented, Parainfluenza/RSV=nonsegmented Antigenic shift: Influenza=yes, Parainfluenza/RSV=no Antigenic drift: Influenza=yes, Parainfluenza/RSV=no |
