Avian influenza, or bird flu, is an infectious virus that spreads among birds.
It affects many species of birds, including chickens, ducks, turkeys and geese. It can be passed between commercial, wild and pet birds. However, not all bird species are affected in the same way.
Bird flu is caused by a flu virus that is closely related to human flu viruses. It is spread through bird droppings, water, feed and equipment.
Like other types of flu, bird flu symptoms include a high temperature, aching muscles and headache.
Since December 2003, there have been many outbreaks of bird flu that have resulted in the death of poultry in countries across Europe, Asia and Africa.
There are 16 types of bird flu, but the type that has caused concern in recent years is the deadly H5N1 strain. The H5N1 virus doesn't infect people easily, although several infections have occurred in humans around the world.
Human cases
As of January 2012, the World Health Organization (WHO) has confirmed there have been 583 cases of H5N1 in humans. These have occurred in Azerbaijan, Bangladesh, Cambodia, China, Djibouti, Egypt, Indonesia, Iraq, Laos, Myanmar, Nigeria, Pakistan, Thailand, Turkey and Vietnam. This had led to 344 deaths.
People who have had bird flu are thought to have developed the virus after coming into close or direct contact with infected birds. Millions of poultry have been killed during outbreaks to prevent the disease spreading and being passed on to people.
Risks
In comparison to the number of birds that have been infected by avian flu, the number of humans who have been infected is very small.
The H5N1 virus does not spread easily to humans and there have been no reports of it passing from person to person.
However, there is a concern that the H5N1 strain may undergo genetic changes that could result in it spreading more easily from person to person, which would significantly increase the risk to humans.
Read more about how bird flu spreads to humans.
Travel advice
There are no travel restrictions for people travelling to affected countries that have been, or are currently, affected by bird flu.
However, it's important to observe the following precautions:
- Avoid visiting live animal markets and poultry farms.
- Avoid contact with surfaces that are contaminated with animal faeces.
- Don't eat or handle undercooked or raw poultry, egg or duck dishes.
- Don't attempt to bring any live poultry products back to the UK.
- Don't pick up or touch dead or dying birds.
- Always follow good personal hygiene practices, including washing your hands regularly.
The Health Protection Agency (HPA) has further travel advice on its website.
Read more about preventing bird flu and managing and treating bird flu in humans.