Avian influenza (bird flu)
Avian influenza, also called bird flu, is an infection in birds caused by several strains of influenza A virus. Avian influenza is found in bird populations worldwide and some of these strains have spread from wild birds to domestic poultry. Some specific viruses (e.g. H5, H7 and H9 strains) have also spread from infected birds to humans, although this is usually rare.
In recent years, human cases have been reported in a limited number of countries, with most previous cases reported from China, Southeast Asia and Egypt, usually following exposure to avian species. However, human cases associated with international travel are very unusual. Check our Country Information pages for recent destination specific news and outbreaks.
In humans, avian influenza symptoms vary, depending on the virus strain. Symptoms range from a mild flu like illness, sometimes with conjunctivitis (red, sore, discharging eyes), diarrhoea and abdominal pain, to a severe respiratory illness with breathing difficulties and pneumonia. Human infections may be fatal.
Prevention
Human infections are mainly associated with direct contact with infected birds or through indirect contact (contact with body fluids, including blood or bird droppings) in places where infected birds have been kept (e.g. poultry farms, bird markets). Transmission from human to human is very infrequent.
Close, prolonged contact with an infected bird is usually needed for bird flu to spread to humans, so all travellers should:
- Avoid visiting live bird and animal markets and poultry farms and do not touch wild or domestic birds (alive or dead).
- Avoid any contact with bird droppings, feathers and nests.
- Do not eat or handle undercooked or raw poultry, egg or duck dishes.
- Wash hands regularly with soap and water or use alcohol-based hand rubs when washing facilities are not available.
Seek prompt medical advice if you become ill with severe breathing difficulties within 10 days of travel to any country affected by avian influenza outbreaks.
The seasonal flu vaccine available in the UK from September/October each year will not prevent infection with avian influenza viruses.
Antiviral medications may be used, after specialist advice, to treat cases or suspected cases of avian influenza.
See UK Health Security Agency website for more information on avian influenza.
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Recent Avian influenza (bird flu) Outbreaks
Influenza A(H5N1) in Mexico
On 2 April 2025, the World Health Organization were notified of a laboratory-confirmed human infection with an avian influenza A(H5N1) virus in the state of Durango. This case represents the second reported human infection with avian influenza A(H5) in Mexico, and the first confirmed case of infection with an influenza A(H5N1) virus in the country. Please see our Topics in Brief article for further details on avian influenza.
Influenza A(H5N1) in Vietnam
On 18 April 2025, the Ho Chi Minh City Department of Health in Vietnam reported a case of encephalitis in an 8 year old child caused by avian influenza A(H5N1). The case is currently isolated and being treated in intensive care. Please see our Topics in Brief article for further details on avian influenza.
Influenza A(H5N1) in United Kingdom
On 27 January 2025, the UK Health Security Agency reported a human avian influenza A(H5N1) case in an individual who had close and prolonged contact with a large number of infected birds. The risk to the wider public is very low. Please see our Topics in Brief article for further details on avian influenza.
Influenza A(H5N1) in USA
During 2024, 66 human cases of H5N1 avian influenza have been detected across 10 US states. 63 cases were exposed during commericial agriculture and linked to outbreaks in dairy herds and poultry. California, Colorado and Washington states have reported the majority of cases. The risk to the general public and travellers remains low. Please see our Topics in Brief article for further details on avian influenza.
