Three pigs which were exhibited at the North Dakota State Fair in Minot last month have all tested positive for a strain of swine flu but it does not appear that the illness has spread to people.

The North Dakota Department of Agriculture reports the three pigs appeared healthy when they were tested on arrival at the fairgrounds, but became ill while at the Fair, according to KX News.

"Fairs and exhibits are an excellent way to showcase livestock and expose the public to animal agriculture production," said Agriculture Commissioner Doug Goehring. "When appropriate precautions are taken, there is minimal risk of spreading disease to the public."

It's the first time a flu virus has been confirmed in pigs at a North Dakota fair, according to the state Agriculture Department.

"Fairs and exhibits are an excellent way to showcase livestock and expose the public to animal agriculture production," state Agriculture Commissioner Doug Goehring said in a statement. "When appropriate precautions are taken, there is minimal risk of spreading disease to the public."

The H3N2 virus was first identified in U.S. pigs in 2010. A surveillance program run by the U.S. Department of Agriculture's Animal and Plant Health Inspection Service found 73 positive tests in fiscal 2011 and 138 in fiscal 2012. It was identified in people in 2011, with 12 human cases in the U.S. that year, 309 cases in 2012 and 19 in 2013, according to the U.S. Centers for Disease Control and Prevention.

Most infections were associated with prolonged exposure to pigs at agricultural fairs, and there has been no sustained spread of the virus, according to the CDC.

Officials say there have been no reported human cases of influenza related to the pigs.