Canada sees early flu activity with H1N1 dominating cases
As the fall season begins, influenza activity in Canada has surfaced significantly earlier than usual, sparking distinct rollout timelines for annual immunizations and causing uncertainty over whether vaccines match currently circulating strains.
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Key Clinical Takeaways:
- National influenza monitoring shows 2,102 detections across Canada since late August, with an early test positivity rate of 3.7 percent between September 20 and September 26, according to cbc.ca data.
- The H1N1 strain accounts for roughly 98 percent of confirmed Canadian cases, while cbc.ca notes that B.C. and Yukon, as well as early urban cases in Toronto and Calgary, are driving the uptick.
- In the United States, NPR reports that flu activity started picking up as early as September in Western states like California, Washington, Hawaii, and Alaska, driven partly by a mutated variant capable of evading existing immunity.
Early Viral Activity Across North America
Passing people on the sidewalk currently, you might get the impression that everyone is coughing and sneezing up a storm. Yet, with public health authorities declaring the arrival of an influenza season sooner than typical, what level of concern is warranted for Canadians? According to national figures cited by cbc.ca, there have been 2,102 detections of influenza across the country since the end of August. Between September 20 and September 26, 3.7 percent of influenza tests came back positive, much higher than the average 0.5 percent rate seen during the same period from 2023 to 2025. Much of this national increase is driven by an uptick of cases in British Columbia and the Yukon, as well as in large cities such as Toronto and Calgary. In Alberta, authorities reported that one person in the 70–79 age range from the Calgary area had died from the virus, with more than 400 confirmed flu cases currently recorded in the province.
A similar unseasonal trajectory has unfolded south of the border. NPR reports that the annual flu season, which typically starts in October or November, began picking up in early September. Dr. Nicole Rivers noted via NPR that seeing flu activity rise this early is very uncommon. NPR reported that flu activity began in Western states such as California, Washington, Hawaii, and Alaska, deviating from the historical pattern where activity typically starts in the South and expands outward.
H1N1 Strain Dominates Canada as Vaccine Matches Well
The biological makeup of this year’s circulating strains differs notably from previous years. Brian Ward, professor emeritus at the Research Institute of the McGill University Health Centre in Montreal, told cbc.ca that roughly 98 percent of cases in Canada so far involve the H1N1 strain. Ward explained that in H1N1-dominated years, outbreaks can be large, but the proportion of people who become very ill is relatively small compared to years dominated by H3N2. Regarding efficacy, Ward told cbc.ca that this year’s vaccine is a good match and is well-positioned to protect against H1N1, noting that H3N2 viruses have not cropped up much in 2026.
In the United States, however, virologists point to viral evolution as the driver of the early surge. Dr. Alex Greninger, a virologist who heads infectious disease diagnostics at the University of Washington, told NPR that doctors there are seeing as much flu right now as they usually would around Christmas. Greninger explained to NPR that a new variant has evolved a mutation that appears to make it better at evading existing immunity, especially among teenagers. Scott Hensley, a virologist at the University of Pennsylvania, emphasized to NPR that it is crucial for people to get an influenza vaccine, adding that this might be a year when individuals want to get vaccinated early.
Canadian Provinces Set Different Vaccine Appointment Schedules
Public health jurisdictions across Canada have adopted varying schedules for deploying influenza and COVID-19 vaccines. Prince Edward Island and Nova Scotia are advising residents that appointments for both vaccines are available now for residents over the age of six months, according to cbc.ca. New Brunswick, Saskatchewan, and Manitoba are allowing residents to book vaccines ahead of official immunization efforts kicking off on October 13.
Concurrently, federal messaging in the United States faces administrative shifts. NPR reported that the Centers for Disease Control and Prevention has not been promoting flu shots as it usually does, noting that Health Secretary Robert F. Kennedy Jr., who oversees the CDC, is a long-time vaccine skeptic. The agency is currently working on an outreach plan intended to deliver transparent details regarding flu immunization alongside other vital measures individuals can utilize during the respiratory virus period to stay safe, incorporating facts concerning both the advantages and hazards of getting inoculated to aid people in making well-considered choices, according to remarks given to NPR by a representative for the CDC.
Meanwhile, COVID-19 rates in Canada are trending lower than last year, with 3.8 percent of tests coming back positive in the final week of September compared to 10.3 percent at the same time in 2025. The National Advisory Committee on Immunizations continues to strongly recommend the latest COVID-19 booster shots for higher-risk individuals, including health-care workers, adults over 65, immunocompromised persons, and residents of long-term care homes.
Disclaimer: The information provided in this article is for educational and scientific communication purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider regarding any medical condition, diagnosis, or treatment plan.