Influenza

Question 1

Influenza family & genome

Answer 1

Orthomyxovirus
4 types - A to D
A to C cause human infection
A & B - 8 pieces segmented (-) SS RNA

Question 2

Haemagglutin & Neuraminidase function

Answer 2

H - facilitate attachment to host cell
N - facilitate release of new virus particles from host cell

Question 3

Antigenic shift and drift

Answer 3

D - mutations in H&N leading to new variants
S - reassortment between 2 distinct flu viruses in same host

Question 4

Classes of drugs for influenza

Answer 4

1. Adamantanes - blocks M2 ion channels of ONLY flu A. Eg - Amantidine. No longer preferred due to high resistance
2. Neuraminidase inhibitors - competitive inhibitors of Neuraminidase of both A&B. Eg - Oseltamavir, Zanamavir.

Question 5

Neuraminidase inhibitors

Answer 5

1. Oseltamavir
2. Zanamavir - not licensed for <5y
3. Peramavir - single dose infusion
4. Laninamivir - Japan

Question 6

Oseltamavir resistance

Answer 6

H275Y mutation in Neuraminidase
Also affects Peramivir but NOT Zanamivir
R292K mutation - Both Oseltamavir & Zanamivir reduced susceptibility

Question 7

Neuraminidase resistance testing

Answer 7

1. Pyrosequencing
2. Digital PCR

Question 8

Newer agents in Flu

Answer 8

1. Baloxavir - inhibits cap-dependent endonuclease (mRNA synthesis)
2. Favipiravir - inhibits RNA dependent RNA polymerase ( NOT licenced)
3. Peramivir - Neuraminidase inhibitor - 600mg IV single dose
4. Laninamivir. NOT licenced

Question 9

R0 for Flu & SRS-CoV-2

Answer 9

1. Influenza - 1.8
2. COVID - 2.6

Question 10

Influenza H & N types

Answer 10

H 1 to 18
N 1 to 11

Question 11

Avian influenza HPAIs & Swine Flu

Answer 11

Avian - H7N9 & H5N1
Swine - H1N1 & H1N2 & H3N2

Question 12

Avian flu PEP

Answer 12

Oseltamavir 75mg OD x 10 days started up to 7 days post exposure

Followed up for 10 days from last exposure

Question 13

Signs of bird flu in BIRDS

Answer 13

1. Sudden death
2. Swollen head
3. Runny eyes
4. Lethargy
5. Unresponsive
6. Lack of coordination
7. Loss of appetite
8. Wing droop
9. Dragging legs
10. Haemorrhage
11. Breathing difficulties
12. Fever
13. Loose stools
14. Drop in egg production

Question 14

Flu treatment

Answer 14

Uncomplicated: healthy - no prophylaxis
At risk: Oseltamavir 75 BD for 5 days/ 10 if immunocompromised

Complicated: Oseltamavir as above/ inhaled Zanamivir 10mg BD for 5 days

Severely immunosuppressed: depends on circulating strain - if strain has higher chances of Oseltamavir resistance, then start Zanamivir for 5 to 10 days

Question 15

Flu vaccine patient groups

Answer 15

1. > 65
2. Pregnancy
3. BMI > 40
4. Children 2 to 17

Question 16

Flu vaccine types, strains & doses

Answer 16

Quadrivalent/Trivalent - 2 subtypes of A + 1 or 2 of B - Victoria +/- Yamagata

LAIV for children - 1 dose intranasal if previously immunised - CAN BE GIVEN WITH OTHER LIVE VACCINES

Inactivated chicken embryo - IM

Question 17

Flu vaccine in children

Answer 17

6mo to 2 years - only for RISK group. Quadrivalent 2 doses 4 weeks apart
2 to 9 - LAIV
9 to 18 - LAIV

Question 18

Highly pathogenic avian influenza (HPAI)

Answer 18

H5N1
Dairy cattle in the USA & persists in raw milk
4 human cases as of 7th July 2024- all mild

Found in wild birds in the UK

Vaccine: AFLUNOV
Surface antigens (H&N) of inactivated of strain - Turkey/2005 H5N1 like strain Clade 2.2.1
Propagated in fertilised hen egg

HAIRS risk - Very low

2 doses recommended in poultry workers and other farm workers >18 years

Conjunctival swab testing recommended by CDC for all suspected cases