Poultry raising systems and highly pathogenic avian influenza outbreaks in Thailand: the situation, associations, and impacts.

Highly pathogenic avian influenza (HPAI), caused by the virus strain H5N1, currently occurs worldwide with the greatest burden in Southeast Asia where the disease was first reported. In Thailand where the disease was first confirmed in January 2004, the virus had been persistent as a major threat to the poultry industry and human health over the past several years. It was generally hypothesized that the main reason for the disease to circulate in Thailand was the existence of traditional backyard chickens and free-range ducks raising systems.