In this Aug. 1, 2012 photo, a participant checks on her pig in the Swine Barn at the Ohio State Fair, in Columbus. (AP Photo/Columbus Dispatch, Kyle Robertson)

A study showing that some pigs that tested positive for swine flu hadn’t yet showed any symptoms isn’t changing health safety plans for the Iowa State Fair under way in Des Moines.

A study released Wednesday says 19 percent of pigs tested at the Minnesota State Fair in 2009 were infected with swine flu but most hadn’t shown the classic symptoms of sneezing, coughing or runny noses.

Iowa State Fair veterinarian Bruce Leuschen told The Des Moines Register there are no plans to test every pig at the fair.

Iowa fair officials typically isolate pigs only after they show the symptoms.

To be shown at the Iowa fair, each animal must have papers from its local veterinarian that attest to the animal’s health.

The fair runs through Sunday.