In 1997, the H5N1 bird flu incident in Hong Kong was the first known instance of a purely avian virus causing severe human disease and death, with 18 human cases, 6 of whom died. The slaughter of 1.5 million poultry in the farms and markets of Hong Kong aborted this outbreak.

This virus (H5N1/97) was in fact a reassortant virus with the HA (H5) being derived from A/Goose/Guangdong/1/96 and the other genes being derived from H9N2 and H6N1 viruses prevalent in quail.