Children’s Hospitals Report Surge in Flu Cases Amid Early Season

Children’s hospitals across Canada are experiencing a significant rise in flu cases as the virus circulates earlier than usual this year. The Children’s Hospital of Eastern Ontario (CHEO) reported an alarming increase, with the number of children testing positive for influenza jumping from 17 cases in November 2024 to 145 cases in November 2025. This represents an increase of over 800 percent in just one year, highlighting the severity of the current flu season.

CHEO has also seen a rise in hospitalizations, with 12 children admitted last month compared to six in the same period last year. According to Dr. Jesse Papenburg, a pediatric infectious disease specialist at the Montreal Children’s Hospital, a national surveillance network tracking 15 children’s hospitals indicates a marked increase in emergency department visits related to flu symptoms.

Doctors are emphasizing the importance of getting vaccinated against the flu now, as it typically takes about two weeks for the vaccine to provide protection. Dr. Papenburg noted that flu season generally impacts school-age children first due to their higher exposure through interactions at school. While these children typically face a lower risk of severe complications, young children under the age of two and those with underlying medical conditions remain at a higher risk for hospitalization.

In addition to the pediatric population, seniors, particularly those aged 75 and older, are also at increased risk of severe illness from the flu. Dr. Papenburg anticipates a rise in emergency department visits and hospitalizations among this age group as the flu season progresses.

Dr. Allison McGeer, an infectious disease specialist at Mount Sinai Hospital in Toronto, pointed out that the current flu virus might be causing more serious infections this year because many people did not have the opportunity to receive their flu shot before the virus began to spread widely in mid-November. In Ontario, the vaccination program for individuals not considered to be in high-risk groups, including children, did not commence until late October.

The circulating flu virus includes both influenza A and B strains, with influenza A typically marking the beginning of the flu season. This year, two strains of influenza A—H3N2 and H1N1—are in circulation, with H3N2 being the dominant strain according to Dr. McGeer. She emphasized the importance of getting vaccinated, stating, “If you’re willing to get a vaccine in one year, this is the year to get it.”

Dr. Papenburg added that H3N2 tends to affect older individuals more severely, as they have developed greater immunity to H1N1 over their lifetimes. Notably, the H3N2 strain has mutated in recent months, potentially reducing its compatibility with the vaccine formulation. “What we’ve seen is that the virus evolved a little bit from the time that the choices were made for the vaccine strains. This H3N2 strain is not a perfect match with what is in the vaccine,” he explained.

Despite this, medical professionals continue to advocate for vaccination. They assert that any level of protection is better than none when it comes to preventing severe illness and hospitalizations. Preliminary data from the United Kingdom suggests that this year’s vaccine provides 30 to 40 percent effectiveness against H3N2 for seniors, and 60 to 70 percent protection for children.

As the flu season progresses, the Public Health Agency of Canada is expected to release its latest flu surveillance data. Health officials are preparing for a continued increase in case numbers throughout December.

This report by The Canadian Press was first published on December 4, 2025. Coverage of health issues by The Canadian Press receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.