What is H5N1 avian influenza?
Influenza A(H5N1) is one of a sub-group of influenza viruses that normally circulate among birds. There are many different strains of avian influenza virus but only a few cause severe disease in poultry and other birds, and even fewer cause infections in humans.
In late 2003, poultry outbreaks of the H5N1 virus were identified in several countries in Asia, and have since been reported from many parts of Asia, the Middle-East, Europe and Africa.
From 2003 through to 7 October 2013, 641 laboratory-confirmed human cases with avian influenza A(H5N1) virus infection had been officially reported to WHO from 15 countries. Of these cases, 380 have died.
Update: 22 November 2013
Only six countries have reported human cases of H5N1 infection in 2013, and only Cambodia is reporting significant numbers of cases. Of the 34 confirmed human cases of H5N1 avian influenza virus reported to date during 2013, a total of 23 have occurred in Cambodia.
All recent cases are considered to be sporadic, with no evidence of community-level transmission. As influenza A(H5N1) virus is thought to be circulating in poultry or wild birds in Cambodia, Indonesia, Vietnam and China, additional sporadic human cases or small clusters are expected in the future.
