Influenza

Question 1

The Flu is caused by the Influenza virus

What is the Flu

Answer 1

An acute viral infection affecting the respiratory tract Nose, mouth, throat, bronchial tubes, lungs)

Question 2

The influenza virus is an Orthomyxovirus.

What does this mean?

Answer 2

Enveloped virus with a Segmented, negative sense RNA genome

Question 3

Describe the 2 surface antigens of the Influenza virus

Answer 3

Haemagglutinin (H): Binds to cell of infected person (18 types)

Neuraminidase (N): Releases virus from host cell surface (11 types)

Question 4

What are the 3 types of Influenza? What hosts do they exist in?

Answer 4

A: In Humans, Pigs, Horses, Birds, Mammals (Main one that causes pandemics)

B: Humans only

C: Humans, Pigs

Question 5

Outline the replication of the Influenza virus in 3 steps

Answer 5

1. Negative sense ssRNA changed into Positive sense ssRNA (via, an RNA-dependent RNA polymerase) and back into multiple Negative sense ssRNAs
2. The original Negative sense ssRNA is changed into mRNA, via an RdRP, then into Viral Proteins
3. Viral Proteins + new negative sense ssRNA-> Nucleocapsids

Question 6

What are 3 methods of transmitting the influenza virus

Answer 6

• Aerosols
• Droplets can infect others directly
• Viral particles can land on surfaces and infect others indirectly

Question 7

Outline how the influenza virus enters a host cell in 3 steps?

Answer 7

1. Haemagglutinin antigen binds to NANA residue on receptor (Sialic acid on a glycoprotein/ glycolipid)
2. Endocytosis occurs
3. Virus released into cytoplasm

Question 8

Outline how the influenza virus leaves the cell in 3 steps

Answer 8

1. Virus buds out of cells
2. Haemagglutinin binds to Glycoprotein on cell surface
3. Neuraminidase cleaves the Glycoprotein allowing the virus to infect another cell

Question 9

Describe the Neurological, Respiratory, GI and Musculoskeletal symptoms of Influenza

(3 for all, except 2 for MSK)

Answer 9

Neurological;

• Headache
• Confusion
• Fever

Respiratory;

• Sore throat
• Dry cough
• Nasal congestion/ runny nose

GI;

• Nausea
• Vomiting
• Diarrhoea

MSK;

• Myalgia
• Fatigue

Question 10

What are 2 methods of treatment of Influenza?
How do they work?

Which types of Influenza can each be used to treat

Answer 10

1. Antivirals;
   - Inhibit viral uncoating after uptake into cell
   - To treat Influenza A
2. Neuraminidase inhibitors;
   - Inhibit viral release from infected cell, cause aggregation of viral particles
   - To treat Influenza A, B

Question 11

What are 2 types of vaccine given for Influenza?

What strains do they protect against?

Answer 11

Formalin-inactivated vaccine;

• (virus inactivated by formalin)
• (Commoner)
• Influenza A, B

Live, cold-adapated vaccine;

• (Inactivated in lower respiratory tract as too warm)
• (Used for kids)
• Influenza A, B

Question 12

Why are there so many mutations in the influenza virus, leading to resistance?

Answer 12

• Virus is constantly replicating and has a life cycle of 6 hours
• The RNA polymerases have a high error rate

Question 13

What is Antigenic drift in Influenza virus?

This is the cause of seasonal epidemics

Answer 13

Accumulation of mutations in the surface antigens Haemagglutinin and Neuraminidase

Question 14

Is Antigenic Shift or Drift shown in Influenza A, B and C

Answer 14

A: Antigenic shift and drift
B: Antigenic drift only
C: Antigenic drift only

Question 15

What is Antigenic shift in Influenza virus?

(This is the cause of seasonal epidemics and pandemics)

(Occurs infrequently, maybe every 10-20 years)

Answer 15

Acquisition of a new type of Haemagglutinin/ Neuraminidase

When 2 or or more types combine