Influenza

Question 1

What causes influenza?

Answer 1

The influenza virus, part of the orthomyxoviridae family.

Comes in groups A, B & C
IfA - mammals and birds
IfB/C - Only affect humans

Question 2

Most influenza is seasonal, occurring during the winter months, why do we think that is?

Answer 2

Several theories:

• Vit D prevents viral infections
• Solar radiation mutates viral RNA creating new strains

Question 3

Describe the structure of the influenza virus?

Answer 3

Two major Surface Antigens:

• Neuraminidase (N) enables new virus release from host cell
• Haemaglutinin (H) enables viral entry to host cell

Question 4

How are new influenza strains produced?

Answer 4

By antigenic drift - small changes to the H/N layout over time hence why we get epidemics and need new vaccines every year

By Antigenic Shift - Abrupt major change to the H/N layout due to combination of 2 strains and reassortment of the viral gene segments –> Creating flu strains that jump species causing pandemics

Question 5

Give an example of influenza antigenic shift?

Answer 5

Combination of Human/Avian influenza to form the swine flu pandemic.

Question 6

How is influenza transmitted?

Answer 6

1) Droplet
2) Direct person-person contact
3) Indirect person-fomite-person contact (the virus can survive 48 hrs on non-porous surfaces)

Avian flu is also transmitted by contact with infected birds (dead or alive)

Question 7

Risk factors for a flu infection?

Answer 7

• Existing disease (neuro/hepatic/renal/cardiac/pulm)
• Immunocompromise incl. DM
• > 65 yrs or <6months
• Pregnancy
• Morbid Obesity

Question 8

How does influenza present?

Answer 8

Abrupt high fever lasting 3 days 
Plus 2 or more of:
- Cough
- Sore throat or rhinorrhoea
- Myalgia
- Headache
- Malaise

Less often they may get N&V + Diarrhoea

Question 9

How do you test someone for Influenza infection?

Answer 9

1) Viral swabs for PCR & molecular detection
2) CXR in case of pneumonia
3) Blood Cultures
4) Pulse Oximetry & Resp rate
5) U&Es, FBC & CRP

Question 10

A major complication of Influenza is Secondary Bacterial Pneumonia, what do we do if we suspect it?

Answer 10

CURB65 Score:

• Confusion
• Urea >7mmol/l
• Resp Rate >30
• BP <60D OR <90S
• > 65yrs`

Question 11

How do we treat Influenza?

Answer 11

If its complicated or at risk e.g. immunosuppressed give them antivirals within 48hrs:
Specifically Neuraminidase inhibitors i.e:
- Oral Oseltamavir (5 days)
- Inhaled Zanamivir (10 days)

Question 12

What defines complicated Influenza?

Answer 12

• Hospitilisation
• Affects the LRT
• Affects the CNS
• Exacerbates an underlying condition

Question 13

How do you treat pregnant influenza?

Answer 13

Oral Oseltamavir

Question 14

At what point is influenza considered non-infectious?

Answer 14

• 24 hrs after the last symptoms
• When anti-viral therapy is completed

Whichever’s last

Question 15

How do we prevent the spread of influenza within hospital?

Answer 15

Staff should use:

• Face masks
• Plastic Apron
• Gloves
• Hand Hygiene

If doing an aerosolising procedure e.g. nebuliser or NIV then use a Gown, Eye protection and a FPP3 respiratory mask.

Question 16

How is the flu vaccine produced?

Answer 16

It changes every year based on the 3 most common strains that year, (2 type A & 1 type B).
Its contraindicated in egg allergies as its grown in chick embryos.

Question 17

What are the major complications of Influenza?

Answer 17

Acute bronchitis & SEcondary Bacterial Pneumonia are the most common.

Also Viral Pneumonia, Myocarditis & Guillain-Barre.

Question 18

Describe the differences between seasonal flu and pandemic flu

Answer 18

Seasonal occurs every winter affecting 10% of the pop and is largely non-lifethreatening in the healthy.

Pandemic flu occurs ~3/century affecting >25% of the pop. and is dangerous with frequent complications.

Question 19

What defines a pandemic?

Answer 19

Effect humans
Be new to the pop.
Show efficient human-human transmission

Question 20

What is an influenza like illness?

Answer 20

A fever and cough that onsets within the last 10 days.

IF its severe enough to warrant hospitlization its called Severe Acute Respiratory Infection (SARI)