influenza

Question 1

types of influenza viruses

Answer 1

influenza A

Influenza B

Question 2

what type is avian influenza

Answer 2

H5N1 type A

Question 3

What is H1N1

Answer 3

swine

Question 4

current who alert for H5N1

Answer 4

is pandemic alert

Question 5

attributes of pandemic influenza

Answer 5

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

Question 6

what is the influenza virus called

Answer 6

orthomyxoviridae

Question 7

what is influenza A

Answer 7

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

Question 8

what is antigenically unstable mean

Answer 8

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

Question 9

what is antigenetic drift

Answer 9

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

Question 10

what is antigenetic shift

Answer 10

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

Question 11

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

Answer 11

no animal reservoir found in humans only

exhibit antigenetic drift so may give rise to epidemics

Question 12

where is influenza c found and how severe is it

Answer 12

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

Question 13

how are influenza viruses defined

Answer 13

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

Question 14

how is the influenza flu vaccine made up

Answer 14

H antigen variability results in epidemic so

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

Question 15

biological features of influenza a virus

Answer 15

ss negative RNA

replicates in nuclues

Question 16

what are the 2 matrix proteins on influenza

Answer 16

o M1 forms a shell around nucleic material

o M2 forms an ion channel in envelope

Question 17

what are the 2 main influenza A surface antigens

Answer 17

H=Haemagglutinin

N=Neuraminidase

Question 18

how does haemagglutinin work

Answer 18

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

Question 19

how many subtypes of neuramindiase

Answer 19

n1-n9

Question 20

how does neuraminidase work

Answer 20

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

Question 21

what caused all the pandemics in the 20th centrury

Answer 21

avian influenza a

Question 22

incubation of influenza

Answer 22

1-4 days

Question 23

how is it spread

Answer 23

• airborne droplets

- contaminated hands

Question 24

how do H and N antigen increase the viruses virulence

Answer 24

• 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

Question 25

what is the cytokine storm

Answer 25

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

Question 26

uncomplicated signs of influenza a flu

Answer 26

``` -chills headache dry cough fever muscular aches malaise anorexia last 5-10 days ```

Question 27

complication of influenza a virus

Answer 27

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

Question 28

what is reye's syndrome

Answer 28

- usually young patients with acute encephalopathy | - cause presumed linked to salicylates

Question 29

how does swine influenza normally present

Answer 29

normally mild disease except 2009 outbreak

Question 30

immune antibody response to influenza

Answer 30

- 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

Question 31

cell mediated immunity to influenza

Answer 31

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

Question 32

lab dx of influenza

Answer 32

- sputum and throat swabs, bal - blood samples - antigen detection - PCR most sensitive

Question 33

how does influenza a multiply

Answer 33

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

Question 34

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

Answer 34

``` 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 ```

Question 35

criteria for classification influenza

Answer 35

- 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

Question 36

what is swine flu made up of

Answer 36

birds prigs and human flu

Question 37

what can swH1N1 be treated with

Answer 37

neuraminidase inhibitors

Question 38

antiviral therapy M2 envelope protein inhibitors 2

Answer 38

 Amantadine and rimantadine | • Resistance is widespread-not used

Question 39

what are the neuraminidase inhibitors

Answer 39

zanamivir and oseltamivir | effective if given with 48 hours from onset of symptoms