H5N1 

"H5N1, killed a wild swan,
It was a kind of omen,
Of everything to come."

Influenza A Virus H5N1, also known as 'Bird Flu' or 'Avian Influenze' , is a subtype of the Influenza A virus, which can cause illness in humans and many other animal species. The bird adapted strain is called HPAI A(H5N1), for 'highly pathogenic avian influenza virus of type A of subtype H5N1'.

One strain of HPAI A(H5N1) is spreading globally after first appearing in Asia, killing tens of thousands of birds and spurring the culling of millions of others. The spread of this strain is being kept in check in farm birds by vaccination. There is some evidence of limited human-to-human transmission, but the spread of the virus from bird to human is inefficient. Still, around 60% of humans knwn to have been infected have died from the virus.

Due to the high lethality and virulence of HPAI A(H5N1), its endemic presence, its increasingly large host reservoir, and its significant ongoing mutations, the H5N1 virus is the world's largest current pandemic threat, and billions of dollars are being spent researching H5N1 and preparing for a potential influenza pandemic.