Like many who had the flu last winter, Piper Long was fighting off feverish hot flashes and shivers that left her bedridden for a week in November.
At first, Long said she thought it was a cold. But when her fever topped 100 F, she said she knew she had taken a turn for the worse.
“It was just awful, like everything was miserable. Your body aches, there’s chills, you’re tired, you can’t think straight,” Long said. “You’re just sick and it’s awful.”
Ottawa was hit particularly hard this flu season.
In November 2025, the Children’s Hospital of Eastern Ontario’s emergency department saw eight times more children test positive for influenza compared to 2024.
“A concerning rise in flu cases at CHEO has led to a significant increase in the number of children coming to the Emergency Department since the start of cold and flu season, with many children needing hospitalization with the flu,” a CHEO statement read.
During the peak months, 40.5 per cent of people tested for flu were positive, a rate four percentage points higher than the Ontario average, according to Ottawa Public Health.
Data from OPH also showed Ottawa recorded a decade-high 257.9 confirmed cases of Influenza A and B per 100,000 people, a rate more than Toronto or the province as a whole.
Earl Brown, an expert in influenza virulence at the University of Ottawa, said the spike in flu cases was because of a mutated strand of the H3N2 subtype and waning vaccination rates. The H3N2 subtype has been dormant since 2022-23, but made landfall again this year.
Brown said this year’s new “subclade K variant” of the H3N2 strand had an abnormal number of mutations and was a vaccine mismatch.
“In normal years you’ll get about one to three (mutations). Five is usually considered a lot. And this one had seven,” Brown said. “This year, there was less protection because the virus had changed more.”
This year’s vaccine was 40-per-cent effective at fending off the new variant — a surprise, Brown said, considering the increase in the number of cases.
Forty-six per cent of Ottawa’s residents 18 and older received the vaccine in 2024-25, with an even lower uptake of 37 per cent of those aged 17 and younger, OPH data shows.
Brown said the new, mutated strain and low vaccination rates created a perfect storm for an influenza surge.
“So along you come with a new virus that can overcome pre-existing immunity. Immunity was already poor because of lack of vaccination,” Brown said. “And we’ve got a very record-breaking year of influenza.”
He added Ottawa likely had a higher rate of positive tests this year because of the city’s older demographic, who are more likely to get tested.
People older than 65 made up 16.6 per cent of Ottawa’s population in 2021, according to census data from Statistics Canada, slightly higher than the proportion of the over-65 cohort in Toronto’s population.
Overall, though, Brown said Ottawa’s not “really an outlier” this year.
“Ottawa is higher than average, but not crazy high,” Brown said. “We’ve got good responsive health care and we detect most of what’s out there.”
In an email to Capital Current, Ottawa Public Health said the method for determining influenza cases has also changed this year. OPH said it’s now reporting cases by postal code through the Ontario Laboratory Information System rather than through the integrated Public Health Information System from past years.
OPH said sometimes hospital postal codes are documented on the flu case lab reports rather than the patient’s personal postal code. With several large hospitals in the region, the public health agency said this might have led to patients from outside Ottawa being counted among the city’s confirmed cases.
OPH added it “encourages residents to stay up to date with vaccination, stay home when sick, and take preventative measures to reduce the spread of illness.”
