The first outbreak of avian influenza(AI) was occurred at breeder farm in 1996 and diagnosed as low pathogenic avian influenza (LPAI). However, the source of infection was not identified. In 1999 and 2000, LPAI was reoccurred at more than 50 poultry farms and now recognized as enzootic disease because of prevalence throughout the country.
In 2001, highly pathogenic avian influenza (HPAI) virus was isolated from duck meat imported from mainland China. This is the first case of isolation HPAI virus from poultry meat and also outside of mainland China. After that, several HPAI outbreaks were occurred in chickens, ducks and other avian species and caused severe economic losses in Korean poultry industry. Although we tried to find out the source of infection, we failed. Migrating water fowl is one of the sources for introduction of avian influenza virus in the domestic fowls. Although we isolated many different subtypes of LPAI or HPAI viruses from the feces of wild birds for several years, we did not find the exact source of infection. We present and analysis the biological characteristics of HPAI viruses isolated for preparation the future pandemic outbreaks in Korea.