Emergency departments in Canada are facing overcrowding due to the rapid spread of influenza, leading to prolonged fevers in both children and adults. The latest federal report indicates a slight decrease in flu activity nationwide. For the week ending on Dec. 27, 2025, 33.3% of tests returned positive results, marking the highest percentage in the last three seasons, as reported by the Public Health Agency of Canada. A federal snapshot on Jan. 3 showed a flu positivity rate of 27.1%.
Various regions in Canada, including British Columbia, Alberta, Ontario, Quebec, and Prince Edward Island, have reported widespread influenza activity. The current surge is primarily driven by the H3N2 subclade, known as K, with mutations that do not seem to cause more severe illness, according to the World Health Organization.
Although some components of this year’s flu shot may not perfectly match the circulating strains, recent studies emphasize that the vaccine still provides protection against other flu subtypes and severe outcomes like hospitalization. Dr. Kevin Wasko, chief of emergency medicine at North York General Hospital, noted a surge in flu cases contributing to increased patient admissions and overcrowding.
In southwestern Ontario, Erie Shores emergency department has seen shorter waits compared to North York but a higher impact on children this flu season. Dr. Braedon Hendy, chief of emergency medicine at Erie Shores Healthcare, highlighted an increase in admissions for influenza type A, particularly affecting pediatric patients.
Reports indicate children experiencing longer fevers and gastrointestinal symptoms due to the current flu strain. Experts suggest that many children have not been exposed to the H3N2 strain, which has not been predominant recently. Wastewater testing in Ontario aligns with clinical observations, showing subclade K as the dominant strain.
Ongoing monitoring will determine if the downward trend in flu activity holds after holiday gatherings. Researchers stress the importance of continued vigilance and adherence to preventive measures to curb the spread of influenza.