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Pulmonology 2 > Clin Med - Influenza > Flashcards

Clin Med - Influenza Flashcards

1
Q

Background history

A
  • Spanish flu pandemic of 1918
  • 3% of worlds population died - more than entire loss of WWI
  • more deaths than all 4 yrs of Bubonic plague
  • US population set back 10 yrs
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2
Q

influenza definition

A
  • infection disease caused by the RNA viruses of the Orthomyxoviridae (affects mammals and birds)
  • 3 genera: A; B; C
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3
Q

general epidemiology of the flu

A
  • 3-5 million cases yearly
  • 250k-500k deaths worldwide
  • 5-20% of US pop. gets flu: 200k hospitalized, 35k die
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4
Q

epidemiology specific to OK

A
  • 2017: 2150 hospitalizations, 68 deaths

- 2018: 253 deaths

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5
Q

infectivity/spread of influenza is primarily through?

A
  • aerosol transmission

- lesser transmission through inanimate vectors and contact (hand shaking etc)

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6
Q

when is a person w/ the flu most infective?

A

-2nd and 3rd days after infection

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7
Q

how long does infectivity of the flu last?

A

about 10 days

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8
Q

virus inactivation

A
  • can survive indefinitely if frozen
  • inactivated at 132 degrees F for a min. of 60 min
  • or by pH <2
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9
Q

influenza A facts

A
  • genus has 1 species
  • wild aquatic birds are natural host
  • most virulent of all 3
  • causes most severe dz
  • seasonal
  • present every year in epidemic and often pandemic outbreaks
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10
Q

how are the flu types are classified

A
  • by their serotypes

- based on Ab reaction to the virus (antigenicity of HA and NA)

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11
Q

influenza virus structure

A
  • all 3 types are similar
  • viral envelope w/ 2 glycoproteins wrapped around a central core
  • central core contains viral RNA genome and proteins
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12
Q

haemagglutinin (HA)

A
  • one of the 2 surface glycoproteins on viral structure

- allows the virus to go inside of the host cell and begin to replicate

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13
Q

neuraminidase (NA)

A
  • one of the 2 surface glycoproteins

- allows virus to break out of the cell

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14
Q

confirmed human** serotypes of influenza A causing pandemics

A
  • H1N1 (Spanish and 2009 flu)
  • H2N2 (Asian flu)
  • H3N2 (Hong Kong flu - genetic drift from H2N2)
  • H5N1 (current threat - bird flu)
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15
Q

non-human subtypes of influenza A

A
  • H16N1 (black headed gulls)
  • H17N1 (fruit bats)
  • H7N7 (highly mutanigenic)
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16
Q

antigenic drift

A
  • slow change over longer period of time d/t small mistakes in replication
  • usually influenza B
  • this is why we can keep some sort of immunity to flu B usually
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17
Q

antigenic shift

A
  • large mutations over a very short period of time
  • usually flu A
  • this is why we have pandemics and why it’s hard to develop vaccines
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18
Q

What is the common link for all types of influenza A?

A

birds

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19
Q

influenza B facts

A
  • only 1 species
  • exclusively infects humans
  • mutates much slower (2-3 times slower) than flu A
  • less genetically diverse
  • only 1 serotype but many strains
  • usually some immunity acquired at an early age
20
Q

influenza C

A
  • 1 species
  • very mild, rarely pandemic
  • only specialty labs do testing
21
Q

How are viruses IDd

A

by their HA and NA

22
Q

influenza trends in 2017 and 2018

A
  • predominately A for first 10 weeks then evenly split b/w A and B
  • of the A viruses:
    2017: 88% H3N2
    2018: 90% H3N2
  • B had little mutation
23
Q

H1N1 typically affects what area?

A
  • upper airways

- to a lesser extent the lungs

24
Q

H5N1 typically effects what area?

A
  • lungs
  • less upper airway involvement
  • more fatal b/c associated w/ pneumonia but not as easily transmitted
25
Q

What is responsible for determining where in the respiratory tract a strain of flu will bind?

A

HA proteins

26
Q

Which strains are easily transmitted b/w people?

A

those that have HA proteins that bind to receptors in the upper respiratory tract

27
Q

what pathophysiology may help explain why healthy people die of the flu?

A
  • cytokine storm/cascade (>150 inflammatory mediators)
  • there is an over reaction of the immune system
  • essentially produces ARDS, airways become constricted
  • body initiates inhibitory feedback so then there’s no response at all
28
Q

Influenza H5N1 frequently cause what type of secondary problem and why?

A
  • viral pneumonia characterized by diffuse alveolar damage and interstitial fibrosis
  • the virus replicates in the alveoli causing them to rupture
29
Q

clinical presentation of the flu

A
  • ***Abrupt onset of fever
  • chills, rigors, shivering
  • cough
  • congestion/coryza/rhinorrhea
  • body aches, myalgia, arthralgias
  • fatigue
  • sore throat
  • HA
  • flushing
  • GI sxs (more predominant in children)
30
Q

What distinguishes the flu from a cold?

A
  • abrupt and sudden onset
  • extreme fatigue
  • lack of GI sxs except in children
31
Q

influenza vaccine

A
  • efficacy varies but always recommended for high risk groups
  • usually trivalent, some quadrivalent
  • inactivated - can’t get flu from it
  • live attenuated vaccine is available (intranasal) - can get flu but very rare
32
Q

What strain is hard to produce a vaccine for?

A

H5N1 - lysed eggs

33
Q

antiviral adamantine class

A
  • amantadine and rimantadine
  • M2 protein inhibitor
  • blocks M2 ion channels to prevent virus from infecting cells
34
Q

adamantine antiviral effectiveness over the different flu types

A
  • some effect against flu A, though resistance is rising quickly
  • no effect against flu B - B does not posses M2
35
Q

Neuraminidase inhibitors

A
  • Oseltamivir (Tamiflu), Zanamivir (Relenza), Peramivir (Rapivab)
  • they prevent viruses from being released from infected cells and subsequently infecting further cells
36
Q

What is the official CDC recommendation for antiviral treatment of influenza?

A

-antiviral tx as early as possible for pts w/ confirmed or suspected flu who have severe, complicated or progressive illness; require hospitalization; or who are at high risk for serious flu-related complications

37
Q

What is “high risk” for getting serious complications from the flu?

A
  • asthma
  • blood disorders
  • chronic lung dz
  • endocrine disorders
  • extreme obesity
  • heart dz
  • kidney/liver disorders
  • metabolic disorders
  • neuro conditions
  • people younger than than 19 on long term aspirin
  • immunocompromised
38
Q

other people at high risk from the flu

A
  • adults 65 or older
  • children younger than 5 but especially younger than 2
  • pregnant women or women up to 2 weeks after end of pregnancy
  • american indians and Alaska natives
39
Q

Tamiflu

A
  • use caution in evidence
  • cochrane review says not significant clinical evidence and possible side effects
  • review this in slides if needed
40
Q

NNT cure of influenza using Tamiflu

A
  • there is no NNT for cure
  • NNT for prophylaxis: 13
  • NNH for vomiting: 14
  • NNH for pysch disturbances in children: 19
41
Q

Peramivir (Rapivab)

A
  • single IV dose, bio-active for 5 days
  • cost to hospital = $950 / dose
  • trial data not released for public review (trial was terminated)
  • official FDA release showed lessening of sxs by 21 hrs
  • not FDA approved for serious flu in patients requiring hospitalization
42
Q

What is the new tx being researched for flu?

A
  • laninamivir octanoate
  • NA inhibitor - still in trials
  • appears to have fewer side effects, lowers viral load and better inhibition of transmission
43
Q

True flu treatments

A
  • anti-pyretics
  • pain meds
  • fluids
  • rest
  • stop smoking
  • treat/avoid pregnancy ladies
  • hand hygiene
  • seclusion
  • hospitalization
  • AVOID abx
44
Q

What strongly determines the virulence of a flu strain?

A

HA proteins

45
Q

What do complications from flu generally occur from?

A

-d/t inhibition of stress hormones couples w/ massive viral replication and inappropriate immune response (cytokine storm)

46
Q

Best offense is a good defense strategy

A
  • annual flu vaccine
  • hand washing
  • covered coughs/sneezes

Pulmonology 2 (17 decks)

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