Influenza Overview

Question 1

Describe the functions of HA and NA as it relates to influenza - how many of each?

Answer 1

Haemaglutinin is a protein responsible for influenza binding to the surface of target cells (i.e. resp epith) and later for the fusion of the viral envelope to the late endosomal membrane

Neuraminidase cleaves terminal sialic acid residues to enable release of the budding virus from cell membrane and prevents clumping together

HA18 N11

Question 2

Complex and larger viruses are able to more easily “____ the species barrier”

Answer 2

JUMP - zoonotic transmission increased

Question 3

What is the leading cause of paediatric viral respiratory disease? And what % does it account for

Answer 3

63% caused by (hRSV) human respiratory syncytial virus

Question 4

Rank influenza species from worst to most mild, and properties of the virus

Answer 4

A is the worst, B can be Bad, C is mild

ssRNA, 13.6kb, 8 segments

Question 5

Influenza:
Annual direct medical cost in US __ bil
Projected lost earnings __ bil

What age groups are most affected?

What usually happens to the virus when a new pandemic arises?

Answer 5

10. 4 bil direct cost
11. 3 bil lost earnings

Children under 4, x4 incidence
Immunity declines with age - elderly

New A subtype appears, causing pandemic

Question 6

Describe 3 mechanisms of viral evolution

Answer 6

1. Antigenic drift (Both fluA+B) - viral polymerase makes mistakes in HA and NA. Still same subtype, but less well recognised by immune system - epidemic
2. Antigenic shift (flu A) reassortment specific to HA subtype - via zoonoses - pandemic
3. Reassortment of segments - host cell needs to be co-infected. E.g. 3 out of 8 new viral segments…

Question 7

3 conditions to start a pandemic

Answer 7

1. New viral subtype emerges
2. It infects humans, causes serious illness
3. Spreads easily and sustainably among humans

Question 8

Compare influenza vs common cold
Pathogen type
Site
Onset
Symptoms
Severity
Mortality
Recovery
Timing

Answer 8

Cause - influenza A&B / many rhinovirus, coronavirus, parainfluenza, metapneumovirus
Site - systemic (fever, arthralgia, myalgia) / local (nose, throat)
Onset - abrupt / gradual
Symptoms - chills, sore throat, cough etc / sneezing, sore throat, nasal congestion
Severity - severe (pneumonia) / mild (pneumonia rare)
Mortality - @risk diabetes, asthma, immunocompromised, 3rd trim pregnancy, post transplantation / very rare
Recovery - 1 to 3wks / 3 to 4 days
Timing - seasonal / year-round

Question 9

Which risk groups are recommended to get the influenza vaccine?

Answer 9

1. Old >65
2. ATSI >50
3. Immunocompromised
4. Chronic disease
5. Healthcare workers
6. 3rd trimester pregnancy (in flu season)
7. Over 6months with medical condition

Question 10

How many hospitalised and deaths estimated in 2017 influenza? Why?

Answer 10

13,500 hospitalised, >3000 deaths particularly Flu A H3, also Flu B

Vaccine less effective against H3 strain - poor i.e. 20%