H1N2

H1N2 is a subtype of the species Influenza A virus (sometimes called bird flu virus). It is currently endemic in both human and pig populations.

H1N1, H1N2, and H3N2 are the only known Influenza A virus subtypes currently circulating among humans.

The new A(H1N2) strain appears to have resulted from the reassortment of the genes of the currently circulating influenza A(H1N1) and A(H3N2) subtypes. The hemagglutinin protein of the A(H1N2) 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.

It is unknown where the A(H1N2) virus originated, but 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 England, Israel, and Egypt. In addition to the virus isolates reported by WHO and PHLS, the Centers for Disease Control and Prevention has identified influenza A(H1N2) virus from patient specimens collected during the 2001-2002 and 2002-2003 seasons. Influenza A(H1N2) viruses have circulated transiently in the past. Between December 1988 and March 1989, 19 influenza A(H1N2) virus isolates were identified in 6 cities in China, but the virus did not spread further.

The H1N2 virus is not very different from the currently circulating influenza viruses. The H1 protein of the H1N2 virus is like the H1 protein of the currently circulating H1N1 viruses and the N2 protein is similar to the N2 protein in the currently circulating H3N2 viruses. The difference is that we don't commonly see the H1 and N2 proteins on the same virus.

The A(H1N2) virus is not causing a more severe illness than other influenza viruses, and no unusual increases in influenza activity have been associated with the A(H1N2) virus. Because both the hemagglutinin and neuraminidase protein on the A(H1N2) virus closely matches the hemagglutinin and neuraminidase proteins of viruses included in the current influenza vaccine, the vaccine should provide good protection against influenza A(H1N2) virus as well as protection against the currently circulating A(H1N1), A(H3N2), and B viruses.