Avian influenza, commonly called the bird flu, is a viral disease caused by Influenza Type A viruses. It is highly infectious and affects poultry birds like chicken, ducks and turkeys. In its milder forms, the virus leads to a drop in egg production while in its more severe forms, it can be lethal. Wild aquatic birds are natural reservoirs of these viruses. As the virus can spread through bird droppings, these birds spread the disease over wide areas as they migrate long distances.