To determine the epidemiology of outbreaks of avian influenza A virus (subtypes H5N1, H9N2) in chickens in Bangladesh, we conducted surveys and examined virus isolates. The outbreak began in backyard chickens. Probable sources of infection included egg trays and vehicles from local live bird markets and larger live bird markets.
The threat that highly pathogenic avian influenza (HPAI) A virus subtype H5N1 poses to poultry and public health has intensified (1). As the virus becomes established in poultry in developing countries, the number of human cases increases (1,2). Countries in the Asian Association for Regional Co-operation are especially vulnerable to virus perpetuation because of insufficient biosecurity, rearing of chickens and ducks together, selling of live birds, and deficient disease surveillance. To prevent human infection with avian influenza (H5N1), knowledge of avian influenza epidemiology is needed. We therefore describe the epidemiology of HPAI outbreaks in chickens in Bangladesh.