Influenza

Question 1

What type of virus is the influenza virus? (DNA or RNA)

Answer 1

RNA virus

Question 2

What are the three main groups of influenza viruses?

Answer 2

Influenza A, B and C

Question 3

What type of animals does influenza A infect?

Answer 3

Mammals and birds

Question 4

What type of animals do influenza B and C infect?

Answer 4

Only humans

Question 5

What types of surface proteins are present on influenza viruses?

Answer 5

Haemagglutinin (H)

Neuraminidase (N)

Question 6

Define antigenic drift

Answer 6

A mechanism of genetic variation within a virus, achieved by small, ongoing point mutations.

Question 7

What is the importance of antigenic drift?

Answer 7

It may change the antigenic properties of a virus, causing worse than normal epidemics and vaccine mismatch

Question 8

Define antigenic shift

Answer 8

The process by which two or more different strains of a virus combine to form a new subtype, resulting in new H/N combinations.

Question 9

What is the importance of antigenic shift?

Answer 9

It enables flu strains to jump from one animal species to another, and with new antigenic properties, the population is unprotected and at risk of pandemics

Question 10

What is the epidemiology of seasonal flu?

Answer 10

Occurs every winter
Affects 10-15% of the population
Usually unpleasant but not life-threatening

Question 11

What is the epidemiology of pandemic flu?

Answer 11

Occurs sporadically
Affects >25% of the population
More serious, more complications

Question 12

What are the three requirements for a pandemic to occur?

Answer 12

• Human pathogenicity
• “New” virus (antigenic shift) - susceptible population
• Efficient person-person transmission

Question 13

What is the incubation period of a typical influenza virus?

Answer 13

2-4 days (range 1-7 days)

Question 14

What are the common symptoms of influenza infection? (7)

Answer 14

• ABRUPT fever of up to 40 degrees Celcius (commonly 38-40 degrees Celcius) which lasts 3 days (range 1-5 days)
• 2 or more of:
  cough
  sore thoat
  rhinorrhoea
  myalgia
  headache
  malaise

Question 15

What are some less common symptoms of influenza infection? (3)

Answer 15

• Nausea
• Vomiting
• Diarrhoea

Question 16

What are the symptoms of swine flu? (8)

Answer 16

• Sudden fever
• Sudden cough
• Tiredness/chills
• Headache
• Sore throat
• Runny nose/sneezing
• Diarrhoea or stomach upset, loss of appetite
• Aching muscles, limb or joint pain

Question 17

How is influenza transmitted?

Answer 17

• Airborne
• Direct contact
• Indirect contact (person > fomite > person)

Question 18

What are the common complications of influenza infection? (2)

Answer 18

• Acute bronchitis

- Secondary bacterial pneumonia

Question 19

How is influenza diagnosed in the laboratory?

Answer 19

Viral nose ant throat swabs

Question 20

What investigations can be done for influenza? (6)

Answer 20

• CXR
• Blood culture
• Pulse oximetry
• Respiratory rate
• U&Es, creatinine and FBC
• CRP (for monitoring recover of pneumonia)

Question 21

What antiviral therapy is usually given for influenza?

Answer 21

Oseltamivir (75mg every 12 hours for 5 days)
or
Zanamivir (10mg inhaled daily for up to 10 days)

NB: use within 48 hours of symptom onset, or ASAP if complicated illness

Question 22

Why should healthcare workers have the influenza vaccination? (3)

Answer 22

• To protect themselves and their families
• To reduce the risk to “at risk” patients
• To reduce absence from work during influenza “surge” activity

Question 23

Which groups are more at risk of influenza infection? (4)

Answer 23

• Any patient with chronic illness (respiratory, cardiac, renal, liver, neurological, diabetes, etc)
• Immunosuppressed patients
• Morbidly obese patients
• Pregnant women (especially in the last trimester)