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Public Health Agency of Canada FluWatch report, which covers the final two weeks of 2017, shows influenza activity keeps rising, hitting those 65 and older the hardest and causing outbreaks primarily at long-term-care facilities.Tero Vesalainen/Getty Images/iStockphoto

Canadian health officials are on "high alert" and bracing for the influenza season to peak as flu activity continues to increase across the country and wreak havoc in other parts of the world.

The latest Public Health Agency of Canada FluWatch report, which covers the final two weeks of 2017, shows influenza activity keeps rising, hitting those 65 and older the hardest and causing outbreaks primarily at long-term-care facilities. So far this flu season in Canada, 11,275 laboratory-confirmed cases have been reported, three-quarters of which were influenza A. Nearly all of the influenza A cases involved the particularly severe H3N2 subtype. More than 1,000 hospitalizations have been reported, and at least 34 people have died, the report says.

Anil Chopra, the head of emergency medicine at Toronto's University Health Network, said a recent uptick in flu-related cases is putting pressure on already resource-strained hospitals, including as it relates to bed shortages and the need to isolate infected patients.

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"I suspect we'll peak in about two weeks, give or take," he said. "It's really too soon to say what kind of season we're having … but [the activity] we're seeing in the emergency department has significantly increased."

Canadian health officials typically look to other parts of the world, such as the Southern Hemisphere and Europe, as a preview of what might happen here. Australia, for example, had one of the worst flu seasons on record during its recent winter months, and Britain is currently in the throes of flu activity so overwhelming that its National Health Service has recommended that hospitals delay all non-urgent surgeries to free-up beds and staff.

"We worry when other jurisdictions are doing so badly," Dr. Chopra said.

While the PHAC report said overall flu activity is within the expected range for the current period, influenza B is circulating much earlier than usual. More than 15 times the number of influenza B detections have been reported this season as compared with the same period during the past seven seasons. The B virus is widely considered less serious than its A counterpart, but a study released last year by the U.S. Centers for Disease Control and Prevention found influenza B caused equally severe disease outcomes.

Over the holidays, the Winnipeg Regional Health Authority saw an increase in flu-related cases, prompting health officials to roll out a slew of overcapacity measures, including opening up extra beds and increasing staffing. Krista Williams, the authority's chief health operations officer, echoed Dr. Chopra in Ontario, saying public-health experts feel strongly that the flu season has not yet reached its height.

"If we see that there are even further increases, like they're suggesting, we are going to deal with that," Ms. Williams said. "We aren't going to be in crisis mode, but we certainly are on high alert and we'll take every action possible to meet the demand." She said local officials are already comparing this flu season with that of 2014-15, a brutal year characterized by a dominant H3N2 strain and a low vaccine-effectiveness rate.

Twice annually – once each for the Southern and Northern Hemispheres – the World Health Organization convenes experts to analyze influenza data and make recommendations on the composition of the vaccine. It is too early to establish the efficacy of this year's flu shot in Canada, but if Australia's experience is any indication, it is likely to prove quite low.

Preliminary estimates for the vaccine's effectiveness against influenza A in Australia has been pegged at roughly 10 per cent, according to a recent New England Journal of Medicine article. That is far lower than the 40 per cent to 60 per cent range seen in years when the vaccine is well-matched to the circulating viruses.

"Influenza, like many other viruses, tends to mutate and change," Dr. Chopra said, explaining the challenges of perfecting a vaccine that must be composed several months before a given flu season begins. "The bottom line is there's a bit of a mismatch [this year]."

He said he has heard from patients, doctors and nurses who have not bothered with the flu shot because of concerns with its usefulness. "The reason to bother is that thousands of people die every year," he said. "Getting the vaccine is better than not getting the vaccine."

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