Bird flu is an infection caused by the avian influenza virus. The virus is found in the intestines of wild birds around the world and while highly contagious is generally not harmful to them. However, some species of domesticated birds (e.g. chickens, turkeys, ducks) are very susceptible to becoming sick and dying from infection.

Bird flu does not generally cross the species barrier and infect humans. However, several cases of human infection with avian influenza A (H5N1) have been reported since 1997. The disease is often fatal with a death rate among reported infections of around 50%. Most infections are believed to be from individuals who have been in close contact with infected birds, though a few cases of human-to-human transmission have been reported.

The risk of catching bird flu is currently considered quite low, but the influenza virus is notorious for its ability to mutate forms. There is fear in the scientific community that the virus may adapt into a form far more dangerous to humans. Scientists are warning of a global pandemic on the scale of the Spanish flu of the early 20th century which killed between 25 and 50 million people worldwide.

Health organizations around the world are treating this as a very serious health risk and researchers are racing to come up with a vaccine.