Bird flu infecting a chicken, conceptual computer artwork. The virus particles are yellow. The deadly H5N1 strain of avian influenza (bird flu) was first detected in South-East Asia in 2003. By early 2006 it had been detected in most Asian and mainland European countries. It is fatal to poultry and many other birds, and can be carried by even more bird species. It can be spread to humans by inhaling the faeces of infected birds, and can be fatal to humans also. It had been responsible for nearly 100 human deaths by early 2006, although it could not at that stage be spread from human to human. It is feared that it might mutate into a form capable of human to human transmission, with devastating consequences.