Known as the Influenza A virus subtype H5N1, or more commonly known as the Avian Flu/Bird Flu, H5N1 is enzootic (maintained within a population) globally in many bird populations. According to recent word from the World Health Organization, as well as the United Nations Food and Agriculture Organization, H5N1 pathogenicity is gradually continuing to rise in endemic areas. However farmed birds are held in check by vaccination, and thus far there is no evidence of sustained human-to-human transmission of the H5N1 virus. The number of worldwide outbreaks being reported are steadily decreasing.