Avian influenza was first identified over 100 years ago during an outbreak in Italy. Since then, the disease has cropped up at irregular intervals in all world regions. In addition to the current outbreak in Asia, recent epidemics have occurred in Hong Kong in 1997-1998 and 2003, in the Netherlands in 2003, and in the Republic of Korea in 2003.

Once domestic birds are infected, avian influenza outbreaks can be difficult to control and often cause major economic impacts for poultry farmers in affected countries, since mortality rates are high and infected fowl generally must be destroyed -- the technical term is "culled" -- in order to prevent the spread of the disease. As a result of the ongoing outbreak in Asia, FAO estimates that around 20-25 million birds had been culled in the region as of 28 January 2004. This figure accounts for less than 1 percent of the region's total inventories, FAO data show. However, the impact can be devastating to local economies and to both commercial poultry operations and smallholders -- particularly in Thailand, where the industry is heavily reliant on trade. In 2003, poultry exports from Thailand accounted for nearly 7 percent of global poultry meat trade, with an export value of approximately US$1 billion.