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infection > influenza > Flashcards

influenza Flashcards

1
Q

types of influenza viruses

A

influenza A

Influenza B

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2
Q

what type is avian influenza

A

H5N1 type A

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3
Q

What is H1N1

A

swine

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4
Q

current who alert for H5N1

A

is pandemic alert

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5
Q

attributes of pandemic influenza

A
  • new strains
  • virulent: severe disease
  • transmits efficiently from human to human
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6
Q

what is the influenza virus called

A

orthomyxoviridae

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7
Q

what is influenza A

A

avian reservoir: aquatic birds are the source but then can also be found in humans and pigs

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8
Q

what is antigenically unstable mean

A

it means you can get antigen drift and shift which can lead to mutation and new variants
- gives rise to the annual outbreaks/epidemics of seasonal flu but then gives rise to pandemic every 10-40 years when bigger change

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9
Q

what is antigenetic drift

A

small changes in antigens affecting H and N antigens due to point mutations

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10
Q

what is antigenetic shift

A

is a major change resulting in new H and N so more likely to become pandemic due to lower immunity.

  • when 2 or more viruses infect and their genes are mixed
  • pandemic potential
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11
Q

where is influenza B reservoir found and what type of antigenically unstable does it show

A

no animal reservoir found in humans only

exhibit antigenetic drift so may give rise to epidemics

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12
Q

where is influenza c found and how severe is it

A

no animanl reservoir only humans soo may exhibit antigenetic drift giving rise to only mild,sporadic resp illness

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13
Q

how are influenza viruses defined

A 
o	The type
o	The host of origin 
o	Geographic origin
o	Strain number
o	Year of isolation
o	H and N designation (for type A only
H3N2 A hong kong/ 03/68
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14
Q

how is the influenza flu vaccine made up

A

H antigen variability results in epidemic so

-seasonal vaccine contains 2 influenza A strains and one or two influenza B strains

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15
Q

biological features of influenza a virus

A

ss negative RNA

replicates in nuclues

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16
Q

what are the 2 matrix proteins on influenza

A

o M1 forms a shell around nucleic material

o M2 forms an ion channel in envelope

17
Q

what are the 2 main influenza A surface antigens

A

H=Haemagglutinin

N=Neuraminidase

18
Q

how does haemagglutinin work

A
  1. usually the one that the immune system targets so changes this molecule to allow the virus to avoid detection which results in epidemics
  2. attaches to resp sialic acid receptors and mediates fusion of virus to cell
  3. avian strains recognise the a2,3 bonds on receptors whilst human recognise a2,6
19
Q

how many subtypes of neuramindiase

A

n1-n9

20
Q

how does neuraminidase work

A

allows the newly created viruses to exit a cell and spread the infection
-ie facilitates budding during egress from host cells by cleaving the glycosidic linkages to sialic acid on virion and host cell surfaces

21
Q

what caused all the pandemics in the 20th centrury

A

avian influenza a

22
Q

incubation of influenza

A

1-4 days

23
Q

how is it spread

A
  • airborne droplets

- contaminated hands

24
Q

how do H and N antigen increase the viruses virulence

A
  • H antigen mediates infection of the respiratory epithelium, progeny virus infects adjacent epithelium
  • N antigen: reduces mucous viscosity and promotes spread to lower resp ract
25
Q

what is the cytokine storm

A

severe influenza A virus strains are thought to trigger a dysregulated immune response resulting in a cytokine storm that leads to severe symptoms eg multi-organ failure

26
Q

uncomplicated signs of influenza a flu

A 
-chills
headache
dry cough
fever
muscular aches
malaise
anorexia 
last 5-10 days
27
Q

complication of influenza a virus

A
  1. pneumonia
    - usually elderly
    - superinfection
    - bacterial agents
  2. Reye’s syndrome
  3. other organs eg gi symptoms
  4. multi-organ failure
28
Q

what is reye’s syndrome

A
  • usually young patients with acute encephalopathy

- cause presumed linked to salicylates

29
Q

how does swine influenza normally present

A

normally mild disease except 2009 outbreak

30
Q

immune antibody response to influenza

A
  • specific to subtype
  • long lived
  • neutralising antibodies against H antigens confer resistance to infection although re-infection with the same virus can occur
  • antibodies against the N antigens reduce disease severity and transmission
31
Q

cell mediated immunity to influenza

A
  • mediated by cytotoxic T lymphocytes that lyse virus infected cells
  • CTLs are usually key players to eradicating and curtailing virus infections
32
Q

lab dx of influenza

A
  • sputum and throat swabs, bal
  • blood samples
  • antigen detection
  • PCR most sensitive
33
Q

how does influenza a multiply

A

multiplies in birds gut and is then excreted in faeces contaminating environment

34
Q

how many of the H/ N subtypes are in humans and how many are in birds

A 
humans=H5N1 Only 
H5N1, H7N3, H7N7, H7N9 and H9N2 
avian influenza A virus strains have so far 
caused human infections
birds= all h and n subtypes
35
Q

criteria for classification influenza

A
  • Fever >38 and lower resp tract symptoms or CXR findings of consolidation or ARDS
    OR
  • Other severe/ life threatening illness suggestive infectious
  • Additionally
    o Exposure 7 days prior to symptoms with a poultry or wild bird
    o Close contact with another human with unexplained resp illness
36
Q

what is swine flu made up of

A

birds prigs and human flu

37
Q

what can swH1N1 be treated with

A

neuraminidase inhibitors

38
Q

antiviral therapy M2 envelope protein inhibitors 2

A

 Amantadine and rimantadine

• Resistance is widespread-not used

39
Q

what are the neuraminidase inhibitors

A

zanamivir and oseltamivir

effective if given with 48 hours from onset of symptoms

infection (15 decks)

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