DES MOINES, IOWA — The U.S. Department of Agriculture’s National Veterinary Services Laboratories (N.V.S.L.) confirmed on Oct. 19 the presence of 2009 pandemic H1N1 influenza virus in a pig sample collected at the Minnesota State Fair submitted by the University of Minnesota. This is the first confirmed find of H1N1 in U.S. hogs.

Additional samples are being tested. As relayed on Friday, three hogs may have screened positive for the novel H1N1 virus at the Minnesota State Fair, U.S.D.A. confirmed on Oct. 16.

An outbreak of 2009 pandemic H1N1 influenza occurred in a group of children housed in a dormitory at the fair at the same time samples were collected from the pigs, but no direct link to the pigs has been made. Information currently available suggests the children were not sickened by contact with the fair pigs. ‘Confirmatory tests’ were conducted on swine samples collected at the 2009 Minnesota State Fair between Aug. 26 and Sept. 1. The pigs sampled at the time showed no signs of illness and were apparently healthy, according to U.S.D.A.

Regarding today’s announcement, sequence results on the hemagglutinin, neuraminidase and matrix genes from the virus isolate are compatible with reported 2009 pandemic H1N1 sequences, U.S.DA. relays. The samples collected at the 2009 Minnesota State Fair were part of a University of Iowa and University of Minnesota cooperative agreement research project funded by the U.S. Centers for Disease Control and Prevention, which documents influenza viruses where humans and pigs interact, such as at fairs.

U.S.D.A. said the infection of the fair pig does not suggest infection of commercial herds because show pigs and commercially-raised pigs are in separate segments of the swine industry that do not typically interchange personnel or animal stock.

"We have fully engaged our trading partners to remind them that several international organizations, including the World Organization for Animal Health, have advised that there is no scientific basis to restrict trade in pork and pork products," said Secretary of Agriculture Tom Vilsack.

Experts also continue to remind the public hogs can contract influenza viruses and that if any of these pigs were confirmed to have the virus, U.S. pork remains safe to eat. People can not contract the novel H1N1 flu from eating pork or pork products because H1N1 flu is not a foodborne disease; it is a respiratory infection that does not impact food safety, U.S.D.A. scientists added.

"Like people, swine routinely get sick or contract influenza viruses. We currently are testing the Minnesota samples to determine if this is 2009 pandemic H1N1 influenza," Mr. Vilsack said. "We are working in partnership with the Centers for Disease Control and Prevention, as well as our animal and public health colleagues and will continue to provide information as it becomes available."