Influenza A H3N2 Variant Viruses (H3N2v)

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Influenza A H3N2 variant virus (H3N2v) is a strain of influenza A that normally circulates among pigs. During 2011, the Centers for Disease Control and Prevention (CDC) reported 12 human cases of H3N2v virus infection. Most infections occurred among persons who had contact with swine, however there was some evidence of limited human-to-human transmission.

During July 1 - August 17, 2012, CDC reported an additional 225 cases of human H3N2v infection from 9 states, including two Wisconsin cases. The severity of human illness caused by H3N2v is similar to seasonal influenza.

The CDC has posted helpful information about the H3N2v outbreak including the national case count, how to prevent infection, information for clinicians, specimen collection and testing guidance, and information for schools, fair managers and swine exhibitors.

Influenza A (H3N2) Variant Virus - CDC


Wisconsin Local Health Departments - Regional offices - Tribal agencies

Thomas Haupt, Influenza Surveillance Coordinator
Wisconsin Division of Public Health 
Bureau of Communicable Diseases
Phone 608-266-5326 | Fax 608-261-4976

Last Revised: January 30, 2017