As influenza rapidly spreads, some emergency departments in Canada are facing overcrowding due to extended fevers in children and adults. The latest federal report indicates a slight decrease in flu activity nationwide. The Public Health Agency of Canada reported that for the week ending Dec. 27, 2025, 33.3% of tests were positive, the highest in the past three seasons. As of Jan. 3, a federal snapshot showed flu positivity at 27.1%.
Various regions in Canada, including parts of British Columbia, Alberta, Ontario, Quebec, and Prince Edward Island, reported widespread influenza activity. The current spike is mainly driven by the H3N2 subclade, called K, which has mutations not linked to more severe disease, according to the World Health Organization.
Although some components in this year’s flu shot may not fully match the circulating strains, the vaccine still provides protection against other subtypes and severe outcomes like hospitalization admissions, as highlighted in a study published in Eurosurveillance. The intense flu season surge has led to increased admissions at hospitals like Toronto’s North York General Hospital.
According to Dr. Kevin Wasko, the hospital’s chief of emergency medicine, the influx of influenza cases has resulted in full capacity and a backlog of admitted patients in the emergency department. Public Health Ontario reported a decline in flu activity over the past two weeks, indicating that the peak occurred in mid-December 2025.
In southwestern Ontario, Erie Shores emergency department has seen more children affected by influenza compared to previous years. Dr. Braedon Hendy, chief of emergency medicine at Erie Shores Healthcare, stated that they have observed a higher number of admissions for influenza type A and increased severity in pediatric cases.
Influenza symptoms range from fever, cough, and fatigue to more severe conditions requiring medical interventions like intubation. Children are experiencing longer fevers with the current subclade K strain. Pediatric infectious disease specialists note that many children have not been exposed to this strain, as it has not been predominant in recent seasons.
The clinical presentation of influenza in Ontario corresponds to wastewater testing results, with subclade K being the dominant strain. Trevor Charles, a microbiology professor at the University of Waterloo, mentioned that the latest wastewater data will confirm if the downward trend reported in Ontario continues after the holiday gatherings.
