Influenza virus

Question 1

Viral family and properties

• Family
• Strand
• Polarity
• Envelope
• Symmetry
• Shape

Answer 1

• Family
  
  • Orthomyxovirus
• Strand
  
  • SS
• Polarity
  
  • Negative sense
• Envelope
  
  • Yes
• Symmetry
  
  • Helical
• Shape
  
  • Linear

Memory aid:

• Otho are influencial people
• SNHeE – BOAR + PF
  
  • ​Single stranded
  • Negative sense
  • Helical
  • Enveloped

Question 2

Components (antigens) and their functions

Answer 2

• Hemagglutinin
  
  • Binds to cell surface receptor [e.g. sialic acid] and promotes viral entry
• Neuraminidase
  
  • Cleaves NA [sialic acid] to release progeny virion from infected cell and degrades the protective layer of mucus in the respiratory tract

Memory aid:

• HE enters
• NEU progeny virions are released

Question 3

Target of neutralizing antibody

Answer 3

Hemagglutinin

Question 4

Species, target and severity

Answer 4

• Type A
  
  • Humans and animals
    
    • Causes pandemic
• Type B
  
  • Humans
    
    • Major outbreak of influenza; does not cause pandemic
• Type C
  
  • Humans
    
    • Mild RTI, does not cause outbreaks of influenza

Question 5

Serotype that cause major outbreak of influenza

Answer 5

Type B

Question 6

Flu vaccines are for this type

Answer 6

B

• Memory aid:*
• B for Bakuna

Question 7

Complication (s)

Answer 7

Patients at risk for fatal bacterial superinfection, most commonly S. aureus, S. pneumoniae, and H. influenzae

Question 8

Roles of pig in pathogenesis

Answer 8

Serve as mixing bowl within which the human, avian, and swine viruses reassort

Question 9

Genetic shift/drift consequence

Answer 9

• Genetic shift
  
  • Causes pandemic
• Genetic drift
  
  • Causes epidemic
• Memory aid:*
• _S_hift is _s_uper, _s_udden, _s_evere (pandemic)

Question 10

Genetic shift/drift is caused by ____

Answer 10

• Genetic shift
  
  • Reassortment of viral genome segments
• Genetic drift
  
  • Minor (antigenic drift) changes based on random mutation in hemagglutinin or neuraminidase genes

Memory aid:

• ReaSsortment
• Segment
• Shift

Question 11

Changes seen in genetic shift/drift

Answer 11

• Genetic shift
  
  • Sudden change in molecular structure à new strain → little or no acquired immunity → new epidemics or pandemics
• Genetic drift
  
  • Slow and progressive change → altered immunological responses and susceptibility
• Memory aid:*
• _S_hift is _s_uper, _s_udden

Question 12

DOC

Answer 12

Oseltamivir or zanamivir

Question 13

Other treatment

Answer 13

Amantadine and rimantadine for influenza A only

Question 14

Rimantadine MOA

Answer 14

Prevent viral uncoating

• Memory aid:*
• Remains coated

Question 15

How many segments of RNA make up the influenza virus genome?

Answer 15

Eight

Question 16

If influenza results in fatal illness, which complication is usually responsible?

Answer 16

Pneumonia caused by bacterial superinfection

Question 17

Random mutations leading to minor genetic changes in the human flu A virus is an example of what?

Answer 17

Genetic drift (antigenic drift)