Several emergency departments in Canada are facing overcrowding due to the rapid spread of influenza, causing children and adults to endure prolonged fevers. The most recent federal report indicates a slight decrease in flu activity countrywide, with 33.3% of tests positive for the week ending December 27, 2025, marking the highest rate in three seasons. Specific regions in British Columbia, Alberta, Ontario, Quebec, and Prince Edward Island reported widespread influenza activity.
The current surge in flu cases is primarily driven by the H3N2 subclade, known as K, although the mutations in this strain do not seem to result in more severe illness according to the World Health Organization. Despite potential mismatches with this year’s flu shot, experts emphasize that the vaccine still offers protection against other flu subtypes and severe outcomes, including hospitalizations, as shown in a UK study published in Eurosurveillance.
At Toronto’s North York General Hospital, the recent flu spike has led to a surge in admissions, resulting in full capacity and patients waiting for beds in the emergency department. Similarly, Erie Shores Healthcare in southwestern Ontario is experiencing increased pediatric admissions related to influenza type A.
Medical professionals have observed children experiencing prolonged fevers and gastrointestinal symptoms due to subclade K. Experts suggest that most children have not been exposed to the H3N2 strain, which has not been prevalent in recent seasons.
In Ontario, wastewater testing aligns with the clinical influenza picture, with subclade K dominating the samples. Ongoing monitoring will determine if the reported decline in flu activity holds true following holiday gatherings.