Since mid-December 2003, a growing number of Asian countries have reported outbreaks of highly pathogenic avian influenza in chickens and ducks. Infections in several species of wild birds and in pigs have also been reported.
The rapid spread of highly pathogenic avian influenza, with outbreaks occurring at the same time in several countries, is historically unprecedented and of great concern for human health as well as for agriculture.
Particularly alarming, in terms of risks for human health, is the detection of a highly pathogenic strain, known as "H5N1", as the cause of most of these outbreaks. H5N1 has jumped the species barrier, causing severe disease in humans, on two occasions in the recent past and is now doing so again, in gradually growing numbers, in Viet Nam and Thailand.
