"Avian influenza is a viral disease that primarily infects birds, both domestic and wild. Certain strains of bird flu break the avian barrier and have been known to infect other animals and humans. Avian flu viruses are common among wild bird populations, which act as a reservoir for the disease. While rarely fatal in wild birds, avian flu is highly contagious and often fatal in domestic poultry, prompting strict biosecurity measures on farms. International trade restrictions imposed by countries to counter avian flu can have large economic effects. The H5N1 strain of highly pathogenic avian influenza (HPAI) has spread throughout Asia since 2003, infecting mostly poultry, some wild birds, and a limited number of humans through close domestic poultry-to-human contact. The virus has spread beyond Asia, reaching Europe in 2005 and the Middle East and Africa in 2006. Over 250 million poultry have died or been destroyed internationally. Human mortality among the more than 275 people infected exceeds 55%. Fears that the virus could mutate to allow efficient human-to-human transmission and cause a human pandemic have prompted a massive political and public health response. Since wild birds can carry the highly pathogenic H5N1 virus, federal, state, and other agencies have increased surveillance of wild and migratory birds. Surveillance is particularly high in Alaska, where Asian and American flyways overlap."
CRS Report for Congress, RL33795