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Pulm > Micro - Influenza > Flashcards

Micro - Influenza Flashcards

1
Q

What key thing distinguishes influenza from other RT viruses?

A

Antigenic diversity

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2
Q

Influenza is (enveloped, nonenveloped) (segmented, nonsegmented) (RNA+, RNA-, DNA)

A

Enveloped segmented (reassortment!) RNA-

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3
Q

What determines an influenza type (A vs. B vs. C)?

A

Nucelocaspid and matrix proteins

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4
Q

What determines the subtype of influenza A?

A

HA and NA

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5
Q

What is unique about influenza C vs. influenza A/B?

A

It is usually asymptomatic, only has 7 genome segments (lacks NA gene)

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6
Q

Most important way to reduce mortality/morbidity of influenza?

A

Yearly vaccination

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7
Q

What is the role of HA?

A

Binds sialic acid on mucus membrane layer of respiratory tract –> virion
ATTACHMENT and PENETRATION

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8
Q

Why the name “hemagglutinin”?

A

Sialic acid also on RBCs, so influenza causes clumping of RBCs

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9
Q

Two sections of HA?

A

Antigenic domain and receptor binding sites

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10
Q

What quality of HA contributes to rapid evolution of influenza?

A

Frequent amino acid substitution

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11
Q

What does NA do?

A

Cleaves neuraminic acid to uncover sialic acid so HA can bind to it; once released from host cell, NA cleaves HA-sialic acid bond so virus can spread

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12
Q

What role does M2 play in virulence?

A

Ion channel on influenza A only that allows H+ influx into endosome which lowers the pH and causes protein dissociation = UNCOATING

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13
Q

What role does NS1 play in virulence?

A

Interferon antagonist and inhibits host cell mRNA processing

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14
Q

Genome of influenza A&B vs. influenza C

A 
A&B = 8 segments
C = 7 segments (lacks NA; maybe this is why it's not as virulent?)
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15
Q

Replication of influenza vs. paramyxoviruses

A

Influenza - nucleus

HSV, hPIV, hMPV - cytoplasm

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16
Q

What causes new pandemic strains of influenza?

A

Reassortment of influenza A genes in a cell co-infected with animal and human strains –> new strain infects human with no immunity

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17
Q

Main influenza A reservoir

A

Avian

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18
Q

What’s unique about avian influenza A?

A

It infects respiratory and GI tracts = can be passed in bird poo

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19
Q

What’s unique about swine influenza A?

A

Avian influenza can’t directly infect humans, but swine can be infected with avian and human strains –> reassortment –> new viruses

20
Q

2 consequences of influenza A populating human and animal species

A
  1. Reassortment –> new pandemic viruses

2. Animal reservoir –> keeps virus circulating even when humans aren’t infected

21
Q

2 reasons influenza is so contagious

A
  1. Viral shedding occurs about 1 day before illness onset

2. Viral titers are highest in first 48 hours, before you know you’re sick and take precautions

22
Q

What causes mortality associated with influenza?

A

LRT complication, i.e. pneumonia

23
Q

Three types of pneumonic complications that can result from influenza infection:

A
  1. Primary viral
  2. Combined viral-bacterial (both at same time)
  3. Post-influenza bacterial pneumonia (after healed)
24
Q

How can one distinguish primary viral from secondary pneumonia?

A
  1. Primary viral pneumonia comes on within 1-4 days; secondary pneumonia comes on 5 days later
  2. Secondary pneumonia will produce purulent sputum and a productive cough, elevated PMNs, and WBCs on PBS
25
Q

What is Reye’s syndrome?

A

Give ASA to reduce fever in kids –> noninflammatory cerebral edema, fatty infiltration of liver, elevated transaminases and ammonia

26
Q

What should be given to reduce fever in kids?

A

Acetaminophen (children’s tylenol)

27
Q

High risk populations for developing complications from influenza illness

A
  1. Preggers - fetal loss/congenital defects especially if infected during 2-3 trimesters
  2. Elderly/immunocompromised - increased viral shedding and duration of illness
  3. Infants/young children - immature immunity; increased risk of pneumonia, encephalitis, meningitis
28
Q

Flu-like sx

A 
Fever
Chills
Myalgia
Cough
Sore throat
HA
Fatigue
Runny nose
29
Q

Describe resolution of sx of flu

A

Systemic sx (chills, fever, etc) subside 3-5 days but respiratory sx (cough, runny nose) persist for weeks

30
Q

Populations with unusual flu presentation

A
  1. Infants/young children: higher fever/convulsions, N/V, abd pain
  2. Elderly/immunocompromised - Fever may be absent or low-grade
31
Q

Sx suggesting viral pneumonia has developed

A

Hemoptysis
Tachypnea
Worsened cough
Dyspnea

32
Q

Sx suggesting secondary pneumonia has developed

A

Purulent sputum, productive cough, recurrence of fever, dyspnea, increased respiratory sx

33
Q

Seasonality of flu

A

Winter to early spring

unless pandemic - irrespective of season

34
Q

Flu incubation period

A

2 days

35
Q

WTF is antigenic drift?

A

Point mutations in HA & NA genes during viral replication due to selective pressures of increased immunity

36
Q

WTF is antigenic shift?

A

Major reassortment of HA +/- reassortment of NA genes when cell is co-infected by animal and human strains

37
Q

How to dx influenza

A
  1. H&P, seasonality
  2. Rapid antigen test
  3. RT-PCR
  4. Culture
38
Q

Who gets inactivated influenza vaccine (Fluzone)?

A

Anyone over 6 months

39
Q

Who gets live attenuated influenza vaccine (FluMist)?

A

Anyone not preggo and 2-49 yo

40
Q

Composition of current influenza vaccines? How long do they provide protection?

A

Two A subtypes + a B virus

2-3 years

41
Q

Who gets antivirals?

A

Pt with severe flu or at high risk for developing complications

42
Q

Two classes of antivirals for use against influenza?

A

Neuraminidase inhibitors

M2 inhibitors

43
Q

List the neuraminidase inhibitors

A

Olsetamivir

Zanamivir

44
Q

List the M2 inhibitors

A

Amantadine

Rimantidine

45
Q

Olsetamivir and Zanamivir are effective against which types?

A

A&B (C doesn’t have NA)

46
Q

Amantadine and Rimantidine are effective against which types?

A

A - only A has M2 channel

47
Q

Which antiviral is associated with >99% resistance thus not recommended?

A

Amantadine

Pulm (33 decks)

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