"We have fully engaged our trading partners to remind them ... that there is no scientific basis to restrict trade in pork and pork products," Vilsack said. "People cannot get this flu from eating pork or pork products. Pork is safe to eat."
Monday's news comes after the USDA announced on Friday that it would test samples from three pigs collected between Aug. 26 and Sept. 1 at the Minnesota State Fair. The samples - from a university research project - showed potential positive tests for H1N1.
USDA officials have said that the pigs did not show signs of sickness, and officials suggested they likely contracted the virus from some of the nearly 1.8 million people who visited the fair.
Officials also said the infection of a so-called show pig doesn't indicate an infection of commercial herds because show pigs are in separate segments of agriculture than the swine industry.
The industry expected that the H1N1 virus would eventually turn up in domestic swine and had enhanced biosecurity measures to protect their pigs from people, said David Preisler, executive director of the Minnesota Pork Board. Herd infections were also already reported in Canada, Australia, Argentina, Ireland, the United Kingdom and Norway. A hog vaccine for the virus is being developed but isn't yet available.
Dave Warner, a spokesman for the National Pork Producers Council, said industry groups would wait to gauge consumer responses, though he said industry officials are at least as concerned about U.S. trade partners reacting adversely to the news. Warner said he would not rule out an ad campaign or other steps to reassure consumers.
Preisler said industry groups have long encouraged pork producers and their employees to get vaccinated for seasonal flu so they don't pass it to their animals, and they're encouraging them to get the H1N1 vaccine when it becomes available.
Infected pigs can pass influenza viruses to other pigs in the same herd. When that happens, producers treat ill animals with aspirin to reduce fever but otherwise generally let the disease run its course through the herd, which Preisler said takes about a week.
After that, he said, they can be safely sent to slaughter or other farms.
Preisler and others in the industry have been stressing that the appearance of H1N1 in domestic swine poses no danger to the public.
"As long as consumers remember that, we're hopeful that it doesn't have a negative impact on the market," Preisler said.
Associated Press writers Steve Karnowski in Minneapolis and Michael Crumb in Des Moines, Iowa contributed to this report.