Influenza

Question 1

Influenza virus

Answer 1

• RNA virus
• 8 segment genomes
• Orthomyxoviridae family
• A, B, C (humans B, C)

Question 2

Pandemic requirements

Answer 2

• Human pathogenicity
• ‘New’ virus - susceptible population
• Efficient person-person transmission

Question 3

Influenza surface proteins

Answer 3

• Haemagglutinin antigens (H1-3) facilitate viral attachment and entry to host cell
• Neuraminidase antigens enable new vision to be released from host cell

Question 4

Antigenic shift

Answer 4

• Two or more strains combine to form a new subtype
• Point mutations of genes coding for antibody binding sites
• May change antigenic (H/N) properties

Question 5

High risk of influenza

Answer 5

• Neurological, hepatic, renal, pulmonary and chronic cardiac
• DM
• Immunosuppression
• > 65 years, <6 months
• Pregnancy
• Morbid obesity

Question 6

Seasonal epidemiology

Answer 6

Winter

• Dec-Feb in North
• Jun-Aug in South

Question 7

Transmission

Answer 7

• Contact (direct/indirect)

- Airborne (droplets)

Question 8

Viral shedding (replication)

Answer 8

• First 4 days of illness

- Longer in children and immunocompromised

Question 9

Virus survival

Answer 9

• Non-porous surface: 24-48 hours

- Porous e.g. tissue: 8-12 hours

Question 10

Incubation period

Answer 10

2-4 days

Question 11

Symptoms

Answer 11

- Pyrexia (3-5 days)
2 or more of (systemic symptoms):
- Cough
- Myalgia
- Headache
- Malaise
GI symptoms less common

Question 12

Complications

Answer 12

Respiratory:
- Acute bronchitis 
- Secondary bacterial pneumonia (CURB65)
- Primary viral pneumonia
Cardiac:
- Myocarditis, pericarditis
CNS:
- Transverse myelitis/ Guillain-Barre syndrome
- Myositis, myoglobinuria

Question 13

Investigations

Answer 13

• Viral nose/throat swabs
• CXR
• Blood culture
• Pulse oximetry
• RR
• U&E’s, FBC, CRP

Question 14

Complicated influenza

Answer 14

Symptoms:

• LRTI
• CNS involvement
• Significant exacerbation of underlying condition

Question 15

Management

Answer 15

- Oxygen (sats <92%)
AVT
- Oseltamivir (oral)
- Zanamivir (inhaled DPI/IV)
- Peramivir 
- Favipiravir 
- Baloxavir Marboxil 
- Amantadine and Rimantadine

Question 16

Oseltamivir antibiotic

Answer 16

- First line for pregnancy 
Side effects:
- GI symptoms
- Headache
- Hallucinations 
- Insomnia 
- Rash

Question 17

Vaccination

Answer 17

• Predicted most likely
• Chemically inactivated and purified
• 2 type A and 1 B
• 0.5 ml IM injection (sore arm)
• Protect self, family, patient and reduce absence