Influenza

Standardization of terminology of the pandemic
A(H1N1)2009 virus

18 October 2011

The pandemic A(H1N1)2009 virus has become a seasonal virus, continuing to circulate with other seasonal viruses since August 2010 when WHO declared the end of the (H1N1) 2009 pandemic. However, the nomenclature of the virus has never been standardized, resulting in diverse names for the same virus. In order to minimize confusion, and to differentiate the virus from the old seasonal A(H1N1) viruses circulating in humans before the pandemic (H1N1) 2009, the Advisers to the WHO Consultation on the Composition of Influenza Vaccines for the Southern Hemisphere 2012, after discussion on 26 September 2011, advise WHO to use the nomenclature below:

A(H1N1)pdm09


This standardization will help to minimize potential confusion among the scientific community as well as the general public.

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