Beware of pigs at county fairs.

• Position: Influenza - Brief article

More than 80% of pigs that tested positive for influenza A virus at county fairs between 2009-11 showed no signs of illness, according to a study by Ohio State University, Columbus. Researchers tested pigs at 53 fairs and found at least one flu-positive swine at almost one-quarter of those events.

The influenza identified includes H1N2 and H3N2 viruses--strains that have been circulating in pigs since 1998. In 2011, all of the H1N2 and H3N2 isolates found in pigs at the fairs contained a gene from the 2009 pandemic strain of H1N1, which is similar to the H3N2 strain causing human illness this flu season.

Though this finding alone is no cause for panic, it does show how quickly influenza viruses can change, notes Andrew Bowman, lead author of the study and a Ph.D. candidate in veterinary preventive medicine.

In a second study led by Bowman, researchers compared the genomic sequences of influenza A viruses recovered in July 2012 from pigs and people. The...