Two human cases of influenza variants normally found in pigs have been detected in Manitoba.
The cases — two different strains — were found in early April in two unrelated individuals in different southern Manitoba communitie, said Dr. Brent Roussin, chief provincial public health officer.
One is a case of human influenza A(H1N2)v and one is a case of human influenza A(H1N1)v.
There is no risk to the public, Roussin said, as the strains don’t transmit easily from human to human.
They were detected after the two individuals independently sought testing after developing an influenza-like illness, Roussin said at a Friday morning news conference.
Both people experienced mild symptoms and fully recovered.
The COVID-19 tests came back negative but the samples were re-evaluated as part of the province’s heightened screening for influenza during the pandemic, and that’s when the strains were further sequenced and identified, Roussin said.
Influenza viruses from pigs do not normally infect humans but they can occur rarely and sporadically, he said.
There have only been 29 H1N2 cases globally since 2005 and none in Canada until Alberta reported one in November.
As for the H1N1 strain, this is only the second case in Canada. The first was in 2012 in Ontario, a news release about the Manitoba case says.
One of the two Manitoba cases has direct exposure to a swine population and the other has indirect exposure. And the two individuals are not connected, either.
For two independent cases to come up around the same time is sheer coincidence, most likely related to the abundance of flu testing being done, Roussin said.
“In most years, when someone has mild influenza symptoms, they wouldn’t even get tested, never mind have those tests sequenced,” he said.
Investigations into the cases are ongoing to determine how transmission may have occurred and to make sure there are no other infections, Roussin added.
“It is certainly possible that this is a true increase in the number of these cases, possibly occurring from exposure to infected pigs or through subsequent, limited human-to-human transmission.”
He said there is no sign of sustained human-to-human transmission at this time.
Reporters asked specifically if the person who had indirect exposure to pigs caught the virus from another individual — a possibility that might not be ruled out by a lack of “sustained” transmission.
“We don’t have details on that right now,” Roussin said, but underscored that there is no risk to anyone.
“We have tested many close contacts and looked at respiratory results from many individuals in the region and have found no other evidence of spread.”
About 170 negative COVID-19 tests from people in that region were re-tested for influenza and all were negative, Roussin said.
The only reason the two cases are being made public is because it’s required under international health regulations, he said.
‘Absolutely safe to eat’
Dr. Scott Zaari, Manitoba’s chief veterinary officer, emphasized on several occasions during Friday’s news conference that people should not be worried about the meat supply.
“Pork is absolutely safe to eat,” he said, and the two cases will have no impact on transportation of pork products across borders.
“I do want to be clear that these viruses are not a food-related illness. It’s not transmittable to people through pork meat or other products that come from pigs.”
He said there has been no epidemiological evidence during the investigation to link the two cases to any particular swine herd.
“What we’ve got is an association. We’ve got indirect and direct contacts with our human patients, but that’s not being found in the swine herd,” he said.
Asked for further details about where the cases were found, Roussin and Zaari wouldn’t narrow it down beyond the massive region of southern Manitoba.
They also wouldn’t provide any information about the setting linked to the cases — whether the pigs were part of a large hog operation or a small farm, or if the direct contact was made through transportation.
They did urge anyone who works with pigs or poultry and has influenza-like symptoms to identify themselves as an agricultural worker to medical officials, including at COVID-19 testing sites, to help identify any potential additional influenza cases.