Causes

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.

Undercooked poultry meat or eggs from infected birds can transmit bird flu. 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 yolks and whites are firm.