Bird flu, which is the lay term for the H5N1 variety of avian influenza, started in Hong Kong in 1997. Since then it has spread to China, Thailand, Cambodia, Vietnam, South Korea, Japan, Taiwan, Laos, Russia, Indonesia, Mongolia, Kazakhstan, Malaysia, Romania, England, Croatia, Macedonia, Kuwait, and most recently to Turkey.

The H5N1 virus has infected many species including ducks, chickens, turkeys, tree sparrows, peregrine falcons, great black-headed gulls, brown-headed gulls, gray herons, Canada geese, bar-headed geese, little egrets, pigs, clouded leopards, white tigers, mice, domestic cats, crows, magpies, peacocks, blue pheasants, rare eagles, turtledoves, swans, terns, and others.

Human infections have occurred in Thailand, Cambodia, Vietnam, China, Indonesia, and now Turkey. Almost all human infections have occurred by humans ingesting blood or insufficiently cooked meat from birds infected with the virus, or being in close contact with sick birds