Since 1997, high-pathogenicity avian influenza (HPAI) virus infection in poultry "avian plague" has emerged as a potential threat to human health, with some fatal cases of bird-to-human transmission. These sporadic infections are caused by H7N7 and H5N1 viruses in Europe and Asia, respectively. The persistence of H5N1 viruses in poultry in several Asian countries, and their appearance in Europe, has raised concerns that the virus might mutate or recombine to create a human pandemic influenza A virus. Wild waterfowl are the natural reservoir of all influenza A viruses, and rarely develop the disease. Since 2002, some H5N1 HPAI viruses have become lethal for waterfowl, cats and humans, indicating an expanding host range. The transmission of H5N1 HPAI viruses from domestic poultry back to resistant domestic and wild ducks and to terrestrial birds (sparrows, pigeons, falcons, etc.) has increased the risk of geographical spread in Asia. These viruses spread through faecal contamination of the environment (particularly groundwater). Low-pathogenicity avian influenza (LPAI) viruses cause localized respiratory and gastrointestinal tract infection and, unlike HPAI viruses, are not detected in blood, muscle or eggs. Detection of HPAI viruses in meat, blood and internal organs of chickens and ducks raises public health concerns and underlines the need to thoroughly cook poultry and eggs consumed in Asia. The last case of HPAI virus infection in France was notified in 1955.