Several cases among a multistate outbreak of variant influenza A(H3N2) may have resulted from swine exposure during an agricultural fair, according to recently published data.

“Variant influenza viruses pose a public health threat because pre-existing immunity in the general population may be low, and current seasonal influenza vaccination may not confer protection against them,” the researchers wrote.

“From January 2005 to June 2012 only 36 cases of variant influenza virus infections were identified in the United States. However, during July 2012 through September 2012, an outbreak of variant influenza A(H3N2) virus involving 10 states resulted in 306 confirmed cases.”