Variant Influenza (Flu)

Influenza viruses that normally circulate in pigs are called “variant” viruses when they are found in people. Influenza A H3N2 variant viruses (also known as “H3N2v” viruses) with the matrix (M) gene from the 2009 H1N1 pandemic virus were first detected in people in July 2011. The viruses were first identified in U.S. pigs in 2010. Infections with H3N2v have mostly been associated with prolonged exposure to pigs at agricultural fairs. Limited human-to-human spread of this virus has been detected in the past as well but no sustained or community spread of H3N2v has been identified at this time. It's possible that sporadic infections and even localized outbreaks among people with this virus will continue to occur. The Centers for Disease Control and Prevention (CDC) continues to monitor this situation closely and will report cases of H3N2v and other variant influenza viruses weekly in FluView and on the case count tables on this website.

Information for Specific Groups
Key Information
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Avian Flu Healthcare and Laboratory guidance

Information and guidance for local and state public health officials regarding the surveillance and investigation of human infections with H3N2v.