Influenza

Question 1

What are the differences between seasonal flu vs pandemic flu?

Answer 1

Seasonal flu:

• occurs every winter
• 10-15% population
• usually not life-threatening

Pandemic flu:

• occur sporadically
• 25+% population
• more serious, more complications

Question 2

What are the requirements for a pandemic flu?

Answer 2

• human pathogenicity
• ‘new’ virus antigenic shift- susceptible population
• efficient person-person transmission

Question 3

What are the clinical features of influenza?

Answer 3

• incubation period 2-4 days
• abrupt fever up to 41°C lasts 3 days
• 2 or more: cough, [sore throat, rhinorrhoea], myalgia, headache, malaise
• systemic symptoms

Question 4

How is influenza transmitted?

Answer 4

• airborne
• person -> person (by large droplets, > 5 microns)
• contact
• direct- person -> person
• indirect- person -> fomite -> person

Question 5

When does virus shedding occur?

Answer 5

• first 4 days
• longer in children + immunocompromised

Question 6

How long does the virus survive on surfaces?

Answer 6

• non-porous- 24-48hrs
• porous- 8-12hrs

Question 7

What are risk factors for complicated influenza?

Answer 7

• disease (neuro, renal, hepatic, pulmonary, chronic cardiac)
• diabetes
• severe immunosuppression
• > 65 yrs
• pregnancy (≤ 2 weeks post partum)
• < 6 month old
• morbid obesity (BMI ≥ 40)

Question 8

What are common complications of influenza?

Answer 8

• acute bronchitis
• secondary bacterial pneumonia (~20%)

Question 9

What are less common complications of influenza?

Answer 9

• primary viral pneumonia
• myocarditis, pericarditis
• transverse myelitis, Guillian-Barre
• myositis, myoglobinuria

Question 10

What are investigations for influenza?

Answer 10

• viral nose + throat swabs
• molecular detection, PCR
• CXR
• blood culture
• pulse oximetry
• RR
• U + Es, FBC, CRP

Question 11

What is the C(U)RB-65 score?

Answer 11

• risk of death in next 30 days (0 = 0.6%, 1 = 3.2%, 2 = 13%, 3 = 17%, 4 = 41.5%, 5 = 57%)
• Confusion
• Urea > 7mmol/L
• RR > 30/min
• BP diastolic > 60 OR systolic < 90
• > 65 yrs

Question 12

What is the management of influenza?

Answer 12

• oseltamivir (tamiflu)
• oral
• 75mg every 12 hrs, 5 days
• zanamivir (relenza)
• dry powder inhaler, IV
• 10mg daily, 10 days
• peramivir
• favipiravir
• baloxavir marboxil