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There are various types of influenza viruses. Avian influenza is caused by those influenza viruses e.g. H5N1, H9N2 and H7N9 that mainly affect birds and poultry, such as chickens or ducks. Since the virus does not commonly infect humans, there is little or no immune protection against it in the human population. If avian influenza virus can spread easily from person to person, an influenza pandemic can occur.
Clinical presentation of avian influenza in humans includes eye infection (conjunctivitis), flu-like symptoms (e.g. fever, cough, sore throat, muscle aches) or severe respiratory illness (e.g. chest infection). The more virulent forms (e.g. infection by H5N1 or H7N9 viruses) can result in respiratory failure, multi-organ failure and even death.
Mode of transmission
People mainly become infected with avian influenza through close contact with infected birds and poultry (live or dead) or their droppings. Human-to-human transmission is inefficient. Outbreaks of avian influenza in poultry have recently been reported in some Asian countries, and some cases of human infection have been reported.
Patients should get adequate rest and drink plenty of fluids. Supportive treatment can relieve symptoms. People with flu-like symptoms should seek medical advice, especially those with weakened body resistance, or if their condition deteriorates, e.g. persistent high fever or shortness of breath. Avian influenza including H5N1 and H7N9 are generally more severe than common flu, and most patients require hospital care. Some anti-viral drugs may be effective in treating the condition. Unless there is bacterial infection, antibiotics should not be used. Aspirin should not be taken by children to avoid the risk of inducing Reye's Syndrome.
Infected birds and poultry (live or dead) or their droppings may carry avian influenza virus. Therefore, members of the public should:
- Avoid touching birds or poultry (live or dead) or their droppings.
- If you have been in contact with birds or poultry, wash hands with liquid soap immediately and thoroughly.
- Cook poultry and egg products thoroughly before eating.
- Avoid touching birds or poultry when travelling outside Hong Kong. Travellers returning from affected areas should consult doctors promptly if they have flu-like symptoms. Inform the doctor of your travel history and wear a mask to help prevent the spread of the disease.
Observe hygiene at all times:
- Avoid touching your eyes, nose and mouth
- Keep hands clean, wash hands frequently with liquid soap, especially before eating, or touching your eyes, nose and mouth.
- Cover your mouth and/or nose with tissue paper when coughing or sneezing. Dispose of the soiled tissues properly, e.g. into a rubbish bin with lid, and then wash hands thoroughly.
- If flu-like symptoms develop, stay at home and avoid going to crowded or poorly ventilated places
At present, there is no vaccine to prevent avian influenza in humans.
Good body resistance helps prevent infections (including influenza). This can be achieved through a balanced diet, regular exercise and adequate rest, reducing stress and no smoking.