Avian influenza is an infection caused by avian influenza (bird flu) viruses, which occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick. However, avian influenza is very contagious among birds and can cause illness and death in some domesticated birds, including chickens, ducks, and turkeys. The virus can transmit from birds to humans, causing lethal infections, bur as yet the virus does not easily transmit from human to human. However, there is a substantial risk of either re-assortment of virus (combination of avian and human influenza), or adaptation of the influenza virus to humans. The present situation in Turkey emphasizes the importance of good surveillance and updated pandemic plans in all countries.