Between May and December of 1997 a novel influenza A virus H5N1 emerged in Hong Kong and caused 6 deaths among 18 confirmed cases. Cases were spread throughout the province. Between March and May of 1997, the virus was detected in three chicken farms, resulting in killing 6,800 birds. The virus was eradicated by quarantine and extermination of more than 17 million birds costing US $60 million in direct and US $250 million in indirect cost (RC6). As most of the surveillance in Hong Kong was conducted in hospitals, there is a possibility that many milder cases may not have been recognized.