A new strain of flu virus diagnosed in at least two Saskatchewan hog farm workers will likely disappear with those cases, but public health authorities need to keep a wary eye on it in case it spreads, a leading Canadian infectious disease expert warns.

Health and veterinary officials on Tuesday reported that two hog barn workers had been ill with a new strain of flu and a third was suspected of having contracted the same strain. All three recovered and animals in the barns were healthy, officials said. (CBC)Dr. Frank Plummer, director of the National Microbiology Laboratory in Winnipeg, stressed that the novel virus is not connected to the pandemic strain of H1N1 influenza A virus that has infected thousands of Canadians and been linked to 38 deaths across the country.

Tests showed two workers at a hog farm in eastern Saskatchewan had been infected with the novel virus last month and a third is suspected to have been sickened by the same agent. All three have fully recovered.

The new flu is a genetic cocktail of seasonal human flu and a long-known animal strain, said Plummer, explaining that an influenza virus that's been "circulating in pigs for many, many years picked up some new genes from the human H1N1 seasonal flu, nothing to do with this pandemic virus."

"And it's created this brand new virus that's never been seen before."

Plummer, in Toronto on Wednesday for a meeting of researchers from across Canada to discuss the H1N1 flu pandemic, said no other human cases of the Saskatchewan virus have been reported and "the pigs apparently look pretty well."

"So, we've picked up this novel virus. We have to react very aggressively to it. But from what we know now, I think it's probably going to end with those three cases and everything will be fine," Plummer said.

The new strain was identified after tests on the workers came back positive for both seasonal and swine flu — a finding that Dr. Moira McKinnon, Saskatchewan's chief medical officer of health, called unusual.

When the aberrant test results were sent to the National Microbiology Lab for further analysis, scientists discovered genes from two different flu viruses had combined.

Plummer said it's not known when this "reassortment" — the mixing of genetic material — occurred, but he believes it's likely the workers were infected by the pigs, not the other way around.

Nor does he think that there was human-to-human transmission because all three workers got sick at the same time. All had been in Saskatchewan for about a year and had not left the province.

"So that would be consistent with coming from a common source like one pig," he said.

While Plummer believes the chance of this new flu virus genetically recombining with the pandemic H1N1 strain is "very, very unlikely," he cautions that public health officials need to aggressively keep on top of the virus.

"We need to understand the extent of the problem: Is it just these three people or is it more than that? Is it just this one pig herd or is it more than that?" he said.