Canada plunges into early flu season as vaccines begin to roll out

Infectious disease experts say Canada’s flu season started about seven weeks earlier than usual this year, but with proper interventions, there is no need to sound the alarm bells just yet.

According to data from Health Canada, 6.1 per cent of tests detected influenza in the week ending Oct. 17.

For the same week in 2025, 0.8 per cent of tests came back positive.

Health Canada defines the epidemic threshold at five per cent, a mark Canada didn’t surpass until mid-November last year.

“It’s still within the range of not being unusual, but it absolutely started earlier,” Dr. Isaac Bogoch, an infectious disease specialist at the University Health Network in Toronto, told Global News.

Bogoch said it is difficult to know exactly why flu season started earlier this year but noted that Australia’s flu season ended later than usual.

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B.C. has been hit particularly hard early in the season with positivity rates between 10 and 15 per cent seen as early as late-September, according to one expert.

“It started also on the west coast of the United States where it’s warmer all the way down in California,” Dr. Brian Conway, medical director of the Vancouver Infectious Disease Centre, told Global News. “So evidently, the virus has entered from the Pacific Rim, perhaps the southern hemisphere that’s ending its flu season and it has made its entry into the West Coast, particularly into British Columbia.”

Doctors say the dominant flu strain this year is of the H1N1 strain, which is what caused the 2009 swine flu epidemic.

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H1N1 is a subtype of Influenza A and spreads the same as any other respiratory virus.

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Bogoch said typically a year dominated by H1N1 sees less hospitalizations than an H3N2 dominant year.

“But I can’t stress this enough, at an individual level, it doesn’t matter. Influenza is influenza is influenza and you might feel really ill,” he said.

South of the border, American health officials have identified a genetic mutation of the H1N1 virus that is spreading amongst the population. The G155E mutation allows the virus to better evade human immunity.

Dr. Jesse Papenburg, an infectious disease specialist at the Montreal Children’s Hospital, told Global News he has not heard of the mutation being in Canada yet, but ultimately it would not change the way that health officials respond.

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“We saw that last year where there was an H3N2 strain subclade K that had very important genetic changes, changes in places that we know are important for the immune system to be able to recognize it,” he said. “At the same time, what we saw in the field was that the vaccines still offered protection that was somewhere in a similar ballpark to what we see usually with estimates ranging from 40 to 60 per cent.”

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The vaccine this year does cover the H1N1 strain, but Papenburg said it is impossible to know just how effective it’ll be until people start getting it.

“The truth is that we will only know how well the vaccine works once we’ve proved enough cases to be able to do interim analyses on vaccine effectiveness in the field,” he said. “People should never be basing their decision on whether or not they should get vaccinated based on the fact of this.”

Regardless of the strains the vaccine targets, Papenburg said what it does reduce is the severity of the illness, decreasing the likelihood of hospitalization or death but almost 50 per cent.

“We’d love to see it higher than that. But at the same time, reducing your risk, especially if you happen to be in one of the vulnerable populations where the risk is already really high, it’s really substantial,” he said.

Most provinces begin launching vaccine appointments around mid-October, but several provinces began offering the shot earlier this year.

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P.E.I. and Nova Scotia began offering vaccine appointments in early October. B.C. began offering the vaccine to vulnerable populations on Oct. 5 and expanded that to all people on Oct. 13. Alberta told pharmacies to start giving out doses as soon as they arrived, ahead of the Oct. 19 launch date.

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Saskatchewan and Manitoba have been offering flu shots since Oct. 13 with Quebec following suit one week later. Ontario is currently offering vaccines to vulnerable populations with eligibility opening to everyone on Oct. 26.