H1N2 is a subtype of the species Influenza A virus (sometimes called bird flu virus). It is currently pandemic in both human and pig populations. H1N1, H1N2, and H3N2 are the only known Influenza A virus subtypes currently circulating among humans. The virus does not cause more severe illness than other influenza viruses, and no unusual increases in influenza activity have been associated with it.
Between December 1988 and March 1989, 19 influenza H1N2 virus isolates were identified in 6 cities in China, but the virus did not spread further. A(H1N2) was identified during the 2001–2002 flu season (northern hemisphere) in Canada, the U.S.A., Ireland, Latvia, France, Romania, Oman, India, Malaysia, and Singapore with earliest documented outbreak of the virus occurring in India on May 31, 2001.
On February 6, 2002, the World Health Organization (WHO) in Geneva and the Public Health Laboratory Service (PHLS) in the United Kingdom reported the identification influenza A(H1N2) virus from humans in the UK, Israel, and Egypt. The 2001-2002 Influenza A(H1N2) Wisconsin strain appears to have resulted from the reassortment of the genes of the currently circulating influenza A(H1N1) and A(H3N2) subtypes. Because the hemagglutinin protein of the virus is similar to that of the currently circulating A(H1N1) viruses and the neuraminidase protein is similar to that of the current A(H3N2) viruses, the seasonal flu vaccine should provide good protection against influenza virus as well as protection against the currently circulating seasonal A(H1N1), A(H3N2), and B viruses.