What is H5N1 Bird Flu and H5N1 Avian Flu?

Definition: H5N1 bird flu, also known as avian bird flu, avian flu and avian influenza, is a subtype of the Influenza A virus, with the H5 and N1 subtypes. Subtypes of the Influenza A virus are designated as HXNY, where H stands for hemagglutinin and N stands for neuraminidase. X is a number that can be one of 16, there is, or can be, H1, H2, H3...all the way up to 16 types of hemagglutinin. And Y is a number that can be 1-9, N1, N2, N3...all the way up to 9.

The most pathogenic subtypes of avian influenza in birds are H5NY or H7NY, although both low pathogenic avian influenza (LPAI) and high pathogenic avian influenza (HPAI) exist for the same subtype. See definition of LPAI and HPAI Bird Flu.

The 1918 pandemic flu strain, sometimes called the Spanish flu, was H1N1 and originated in birds. In fact, all HXNY subtypes of Influenza A are thought to have originated in birds, although many subtypes are now human influenza viruses. Today H1N1 is one of the seasonal flus, and since many people are thought to have some resistance to H1, it mostly causes complications in very old or very young people.

The H5N1 avian flu virus circulating in Asia, Africa and parts of Europe, also known as Asian bird flu, has killed 59% of the more than 250 people it has infected. It is a new virus to humans and probably just a handful of people are immune which is why virologists such as Robert Webster fear an imminent pandemic. Fortunately, until now, H5N1 in humans has not been very contagious.

More information:

• Bird flu and bird flu symptoms
• Updated Bird Flu Case Report

Also Known As: bird flu, avian influenza, HPAI bird flu