South Asian Health Support Programme

What is influenza?

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• Influenza is caused by a virus that attacks mainly the upper respiratory tract – the nose, throat and bronchi and rarely also the lungs

• Hospitalization and deaths mainly occur in high-risk groups (elderly, chronically ill)

• More prevalent in January-March and July-August each year in HK

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Type of influenza

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Three types of influenza viruses are recognized: A, B and C

The currently circulating influenza viruses that cause human disease are type A and B

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Type A

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• Influenza A has 2 subtypes which are important for humans: A(H3N2) and A(H1N1), of which the former associated with most death.

• It is infectious to mammals e.g. pig, birds and human

• Emergence of new subtypes occurs from time to time at irregular intervals

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Type B

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• Also common in HK and is infectious to human only

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Type C

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• Less commonly seen in HK

• Can be epidemic 

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Causes - How is influenza transmitted?

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• Via air droplets

• Small particles from cough and sneeze

• The influenza virus enters the body through the nose or throat

• Disease spreads very quickly among the population especially in crowded circumstances

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Clinical symptoms

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• Incubation period around 1 to 3 days

• Three main symptoms, namely fever, sore throat and cough

• Headache, muscle pain, runny nose and other symptoms like tiredness, diarrhea and vomiting may also appear

• Usually self-limiting with recovery in 2 to 7 days

 

Difference between influenza and common cold

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Managing influenza

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• Infected persons should take adequate rest and drink plenty of water

• Antiviral agents can reduce the severity and duration of illness e.g. amantadine is effective for strains of influenza A    

• Antibiotics are unnecessary unless influenza is complicated by bacterial infection

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Prevention of Influenza

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• Maintain good personal and environmental hygiene.

• Build up body resistance by balanced diet and regular exercise

• Avoid crowded environment during flu season

• Vaccination - Recommended to receive each year to maintain the protection

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Who should not receive the vaccine?

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• Individuals with egg protein or vaccine components allergies

• With fever or infection on day of vaccination

• Infants under 6 months old