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Infection and Immunity > Influenza > Flashcards

Influenza Flashcards

1
Q

What are synonyms of influenza?

A

Flu, grippe

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2
Q

How is influenza spread?

A

By aerosols very efficiently

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3
Q

What is influenza?

A

An acute viral infection involving the respiratory tract

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4
Q

What is the incubation period of influenza?

A

1-3 days

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5
Q

How long does influenza last?

A

3-10 days

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6
Q

What does infection lead to?

A

Cell killing and local inflammatory responses

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7
Q

What happens after cell killing?

A

Chemokines and cytokines (macrophages) that cause the symptoms: fever, muscle ache, headache, prostration, anorexia. ‘Cytokine storm’

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8
Q

Is death from primary infection of influenza common?

A

Death from primary infection is rare.

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9
Q

Is death from secondary infection of influenza common?

A

Cell damage predisposes to secondary bacterial infections with deaths, especially in the elderly

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10
Q

What was the mortality rate of the Spanish flu?

A

Mortality rate was 2.5% compared to previous epidemics of 0.1% i.e. more than 20x higher

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11
Q

How many deaths were there due to the Spanish flu?

A

> 40 million deaths (could have been up to 100 million?)

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12
Q

What was the 1918 pandemic virus caused from?

A

Virus genome sequenced from permafrost burials

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13
Q

Whats the originator of HA virus?

A

Birds

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14
Q

When were the genetic elements of the 1918 virus estimated to be circulating from?

A

1911

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15
Q

What is done to understand the pathology of pandemoc viruses?

A

Partial reconstruction used in animal experiments

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16
Q

What are the 3 distinct serotypes?

A

A type
B type
C type

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17
Q

What is the A type serotype?

A

Viruses infect mammals, including humans, horses, pigs, ferrets and birds. Cause epidemics and pandemics

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18
Q

What is the B and C type serotype?

A

B- and C-type viruses infect only humans & are not as severe as A types
(some evidence of B in horses, and C in dogs and pigs)

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19
Q

What are the important reservoirs in generating new viruses?

A

Pigs and birds

20
Q

What is the structure of the virion?

A

Lipid envelope with 2 projecting glycoproteins
Envelope inner side is lined by matrix protein (M1)
Inside are 8 ribonucleoprotein (RNPs) genome segments
Lacks RNA proof-reading enzymes
Not a retrovirus- no DNA step, no genome integration

21
Q

What are the 2 glycoproteins in the lipid envelope?

A

Haemagglutinin (HA), a trimer

Neuraminidase (NA), a tetramer

22
Q

What are the 3 important genome segments- RNA encoding?

A

Haemaglutinin- major antigenic glycoprotein
Neuraminidase- virus release
Matrix- major virion component

23
Q

What are the serotypes of influenza virus?

A

15 HA and 9NA

24
Q

What is the nomenclature of influenza virus strains?

A 
A (type)
Singapore (town)
6 (first isolated number of isolates)
86 (year of isolation)
(H1N1) type of HA and NA
25
Q

What happens when a strain goes under minor changes?

A

Absence of RNA proofreading enzymes, the RNA-dependent RNA polymerase that copies the viral genome makes an error roughly every 10 thousand nucleotides, which is the approximate length of the influenza vRNA

26
Q

What happens when a strain goes under major changes?

A

Every 10-15 years worldwide a new pandemic strain appears in humans with a totally new HA and sometimes a new NA (‘antigenic shift’)

27
Q

What do changes to strains do?

A

Enhance the virus’s ability to infect host & evade the immune system

28
Q

What do separate genome segments facilitate?

A

Genetic exchange between different strains. Reassortment (very rarely recombination)

29
Q

What does exchange of genes cause?

A

New combinations of HA and NA to be expressed on the viral envelope

30
Q

What are antigenic ‘drift’ minor changes?

A

Minor mutations in one or more of 4 HA regions
Genome is (-) RNA so mutation/error rate is high
Single amino acid substitiutions accumulate that evade antibody specific to previous strains/infections
Effects are evident over 2-3 years
Occurs in all A,B and C strains

31
Q

What is 1 of the major changes of antigenic shift?

A

A new HA is acquired (plus sometime new NA) that is crucial for infection & cell entry
Exclusive to A strains
Enables influenza virus to cause pandemics

32
Q

What is the 2nd of the major changes of antigenic shift?

A

Uses ‘mixing vessels’ e.g. pigs that are susceptible to both bird & human strains
Complete genome segments can be exchanged between these viruses if they infect the same cell
•New recombinant virus

33
Q

What does H5N1 cause?

A

Lethal bird flu, deciminating flocks of domestic poultry

34
Q

How many people were infected with H5N1 in 2015 and how many deaths were there?

A

638 infected

379 deaths

35
Q

Why does the H5N1 virus fizzle out?

A

Virus is not (yet) adapted to humans

36
Q

What position is H5 HA and what does this mean?

A

Has glutamine at position 226- i.e. is avian and poorly adapted to humans. But, with a single mutation to HA226 leucine (as in human viruses) big trouble

37
Q

What are other strains of avian influenza viruses?

A

Many subtypes, 4 of which are highly pathogenic humans- H5N1, H7N3, H7N7, H7N9 and H9N2

38
Q

What is the treatment with M2 inhibitors?

A

Amantidine and rimantadine drugs are active against most A strains
Bind M2 protein
Drug- treated cells cannot lower the pH of endosomes causing uncoating, an M2 function

39
Q

What does treatment for M2 inhibitors work for?

A

A-type viruses

40
Q

What is treatment of neuraminidase inhibitors?

A

11 universally conserved amino acids form the NA active site. Synthetic sialic acid analogues are NA enzyme inhibitors

41
Q

What does neuraminidase inhibitor treatment work for?

A

Against all A and B strains

42
Q

What types of viruses are required?

A

HA type

43
Q

What is required for a virus?

A

Large amounts are grown in embryonated eggs (cheap and efficient) purified and formalin inactivated

44
Q

How much protection does the influenza virus vaccine give?

A

60-80%

45
Q

What do the WHO have to do every year in regards to creating a vaccine?

A

A decision must be made in August as to which HA type to use the following winter. A monitoring system worldwide helps make this decision
WHO recommends strains that should be targeted in the following winter’s vaccines.

46
Q

How many combinations of genes for influenza are possible?

A

256 combinations

47
Q

Who is the flu vaccine normally given to?

A

Live attenuated (temperature- sensitive) flu immunisation, up nose, for children up to 5 or 6

Infection and Immunity (23 decks)

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