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Influenza A(H1N2) Viruses
NOTE: This document is provided for historical purposes only and may not reflect the most accurate and up-to-date information on this subject. For current flu information, please visit the CDC Flu Homepage.
On February 6, 2002, World Health Organization (WHO) and the Public Health Laboratory Service (PHLS) in the United Kingdom reported the recent identification of a new influenza virus strain, influenza A(H1N2), isolated from humans in England, Israel, and Egypt. In addition to the viruses reported by PHLS, the Centers for Disease Control and Prevention (CDC) has identified influenza A(H1N2) virus from patient specimens collected during the 2001-02 and 2002-03 seasons. Influenza A(H1N2) viruses have been identified in the past. Between December 1988 and March 1989, 19 influenza A(H1N2) viruses were identified in 6 cities in China, but the virus did not spread further.
Influenza type A viruses are divided into subtypes on the basis of two proteins, hemagglutinin (H) and neuraminidase (N), on the surface of the virus. Since 1977, two influenza A virus subtypes, A(H1N1) and A(H3N2), have circulated widely among humans. The new 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. Because the current influenza vaccine contains strains with both H1 and N2 proteins similar to those in the new strain, the current vaccine should provide good protection against the new A(H1N2) virus. No unusual levels of disease have been associated with this virus and, at this time, it is uncertain if the A(H1N2) virus will persist and circulate widely.
International influenza surveillance conducted through WHO and U.S. surveillance conducted by CDC will continue to track the occurrence of A(H1N2) viruses.
Other Links:
- Page last modified December 5, 2003
- Content Source: Coordinating Center for Infectious Diseases (CCID)
- National Center for Immunization and Respiratory Diseases (NCIRD)
