H3N2 found in most pigs tested following human cases

Aug 7, 2012 (CIDRAP News) – A high proportion of pigs tested for H3N2 influenza in connection with recent human cases of variant H3N2 (H3N2v) in Indiana and Ohio have been found to carry the virus, according to figures from state officials.

About 30 people in the two states have had confirmed H3N2v infection in the past few weeks, most of them in connection with county fairs, according to previous reports. The virus carries the M or matrix gene from the 2009 H1N1 virus, which may increase the strain's ability to jump from pigs to humans, according to health officials.

Denise Derrer, a spokeswoman for the Indiana State Board of Animal Health, said today that 29 of 30 pigs that were tested in connection with three recent county fairs had the virus.

Twelve of 12 pigs from the LaPorte County Fair in northwestern Indiana tested positive, Derrer told CIDRAP News. Four human cases were linked to the LaPorte fair in late July.

Also, 9 of 10 pig samples tested from the Monroe County Fair in Bloomington were positive, she reported. The swine barn at the fair was closed last week because of illness among the pigs, and several people who had flu-like symptoms were tested for the virus.

The US Centers for Disease Control and Prevention has confirmed cases in two of those people, Monroe County officials said in a press release today. It was not immediately clear if those cases were among new cases mentioned yesterday by an Indiana State Department of Health official.

Derrer also said that 9 of 10 pigs that were tested in connection with the Washington County Fair in south-central Indiana were positive for the virus. She said some people who attended that fair also are being tested, but she was not aware of any confirmed human cases there as yet.

Derrer also noted that a number of pigs were sent home from the Indiana State Fair a day earlier than scheduled because they had temperatures above 105ºF. The pigs were being monitored, and yesterday five pigs passed that level. "Since all the 4H shows were done, and with the temperatures in the barn, we thought it was prudent to get them out," she said.

Fair and 4H officials agreed with the board's recommendation and sent the pigs home a day ahead of schedule, she added. Test results on those pigs are pending, she said.

In Ohio, two pigs from the Butler County Fair were tested and found positive, according to Erica Pitchford, communication director for the Ohio Department of Agriculture. Results were still pending on one pig that was at the fair. Previously, 14 human cases were reported in people who attended the Butler County event.

Last week Ohio officials reported that two pigs shown at the Ohio State Fair tested positive for the H3N2 strain. Pitchford said today that one of those cases was confirmed and the second is currently considered a likely case.

"We couldn't say we had full confirmation [on the second one], because the sample was not large enough for a full sequence, but what we were able to match, we did," Pitchford said.

Because of the recent human cases, federal and state officials have warned the public to take precautions to avoid catching the virus if they visit swine barns at fairs this summer.

See also:

Aug 7 Monroe County, Ind., press release

Aug 2 Ohio Department of Agriculture press release

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