Influenza

Question 1

Aetiology of influenza

Answer 1

RNA viruses of the family orthomyxoviridae (influenza viruses)
Transmission: air droplets from coughing or sneezing, transmission via nose, mouth, and eyes.
Influenza viruses can live for several hours on toys, doorknobs, computer keyboards, surfaces or furniture

Influenza A: Occurs more frequently and is more virulent. Responsible for local outbreaks, larger epidemics or pandemics
Influenza B: Often co-circulates with influenza during yearly outbreaks. Generally less severe, may be responsible for outbreaks
Influenza B: mild or asymptomatic infection similar or the common cold

Question 2

Risk factors for influenza

Answer 2

Chronic illness e.g. neurological, respiratory, cardiac, haematological
Genetic condition e.g. Down’s syndrome
Premature birth
Immunosuppression
Winter months

Question 3

Symptoms of influenza

Answer 3

Coryza, nasal discharge
Cough
Fever
GI symptoms: anorexia
Headache, malaise, myalgia, arthralgia
Photophobia, conjunctivitis, lacrimation and pain upon eye movement
Sore throat

Complicated: Increased work of breathing | presence of LRTI (hypoxia, dyspnoea, lung infiltrate) | CNS involvement | significant exacerbation of an underlying medical condition

Question 4

Investigations for influenza

Answer 4

Investigations are done if (1) there are risk factor for severe disease (2) they have presented within 48h of onset

Nasal/throat swab/NPA for PCR: +ve

Question 5

Management for influenza

Answer 5

Previously healthy → no antiviral indicated
Supportive:
- Rest
- Adequate fluids
- Paracetamol/ibuprofen
- Mist humidifier

<48h since onset + “at risk” → antiviral (PO/NG Oseltamivir (neuraminidase inhibitor)

Question 6

What makes someone at risk for influenza

Answer 6

<6 months
Chronic respiratory disease e.g. CF
Uncontrolled asthma
Previous admission for LRTI
Congenital heart disease
Chronic kidney disease
Chronic liver disease
Chronic neurological conditions
DM
Immunosuppression

Question 7

Complications of influenza

Answer 7

Acute bronchitis
Exacerbation of asthma
Otitis media
Pneumonia
Sinusitis
Cardiac complications: myocarditis, pericarditis, exacerbation of underlying cardiac disease
Febrile convulsions
Myalgia, myositis and rhabdomyolysis
Neurological complications - Reyes syndrome, encephalomyelitis, transverse myelitis, Gullain-Barre syndrome, aseptic meningitis, and encephalitis
Toxic shock syndrome

Question 8

Prognosis for influenza

Answer 8

Most people recover without serious complications
Fever and muscle aches usually last only 2 to 4 days, but cough and tiredness may go on for 1 to 2 weeks or more