The first avian influenza virus to infect humans directly occurred in Hong Kong in 1997, during an avian flu epidemic on the island. This outbreak was linked to chickens and classified as avian influenza A (H5N1) or bird flu.
Bird flu occurs naturally in wild waterfowl and can spread into domestic poultry, such as chickens, turkeys, ducks and geese. The disease is transmitted via contact with an infected bird’s feces, or secretions from its nose, mouth or eyes.
Open-air markets, where eggs and birds are sold in crowded and unsanitary conditions, are hotbeds of infection and can spread the disease into the wider community.
According to the Food and Drug Administration, bird flu cannot be transmitted by eating properly cooked poultry meat or eggs from infected birds. Poultry meat is safe to eat if it’s been cooked to an internal temperature of 165 F (74 C). Eggs should be cooked until the yolk and white are firm.