Experience in control of avian influenza in Asia.

Highly pathogenic H5N1 avian influenza viruses have been circulating in Asia for over ten years, providing considerable experience on which to base appropriate long-term strategies for their control. Experience in Hong Kong SAR demonstrates that existing production and marketing practices should be changed and a range of parallel measures used. It also shows the extent of surveillance required to ensure continuing freedom from infection. Certain high-risk practices should be changed or otherwise overcome in order to control and prevent disease, including intensive rearing of large numbers of poultry in premises without biosecurity commensurate with the level of risk for exposure; complex market chains involving many smallholders selling poultry through large numbers of transporters and middlemen in poorly regulated live poultry markets; and rearing of large numbers of ducks outdoors. These high-risk practices are compounded by weak veterinary services and poor reporting systems. In many parts of Asia, these methods of rearing and marketing are an integral way of life, support the poorest members of the community or cannot be changed quickly without severe socioeconomic consequences. The gains made so far will be ephemeral unless there is a shift from an emergency focus to one of consolidation in which these high-risk practices are identified and sustainable measures implemented to minimize the risks they pose, taking account of the socioeconomic effects of interventions. Vaccination will play a key role, as it currently does in China and Viet Nam.