Influenza A Virus Subtype H5N1 (H5N1)

H5N1 pathogenicity is gradually continuing to rise in endemic areas, but the avian influenza disease situation in farmed birds is being held in check by vaccination, and so far there is "no evidence of sustained human-to-human transmission" of the virus. Several H5N1 vaccines have been developed and approved, and stockpiled by a number of countries. HPAI A(H5N1) is considered an avian disease, although there is some evidence of limited human-to-human transmission of the virus. A risk factor for contracting the virus is handling of infected poultry, but transmission of the virus from infected birds to humans has been characterized as inefficient. Still, around 60% of humans known to have been infected with the current Asian strain of HPAI A(H5N1) have died from it, and H5N1 may mutate or reassort into a strain capable of efficient human-to-human transmission.