Early Season Dynamics
The strain composition driving early cases varies by region. In Canada, influenza A(H1N1)pdm09 accounts for roughly 98% of cases so far. Brian Ward, a professor emeritus at the Research Institute of the McGill University Health Centre, noted that years dominated by H1N1 typically feature large outbreaks, but the proportion of patients who become severely ill is relatively small compared to seasons dominated by the H3N2 strain.
“So far at least, this looks like an H1N1 dominated year,” Ward said. “I’m not convinced yet that we’re actually seeing the beginning of a real outbreak. What we’re seeing is sort of isolated, small outbreaks.” This contrasts with the recent experience in the United States, where last winter saw an unprecedented flu epidemic fueled by the highly mutated H3N2 subclade K variant, often referred to as “super flu.” That season was one of the worst in decades, with doctor visits for flu-like illness reaching levels not seen in over 25 years.
Global Vaccine Updates
As seasonal influenza activity rises, the World Health Organization (WHO) has announced its recommendations for the viral composition of influenza vaccines for the 2027 southern hemisphere influenza season. These recommendations, developed following an international consultation, are used by national regulatory agencies and pharmaceutical companies to develop, produce, and license vaccines for the upcoming season.
From February to August 2026, influenza A(H1N1)pdm09, A(H3N2), and influenza B viruses circulated in varying proportions globally. Influenza A viruses were the most common in most regions, with the exception of Northern and Western Africa, North America, and Eastern Asia, where influenza B viruses dominated. The WHO’s Global Influenza Surveillance and Response System (GISRS) continues to monitor these trends, with experts convening twice yearly to review surveillance data and recommend vaccine compositions.
Dr. Maria Van Kerhove, WHO’s Director for Epidemic and Pandemic Management, emphasized the importance of this global collaboration. “The commitment of countries and laboratories to share data, viruses and expertise enables WHO to make timely vaccine recommendations, strengthening our collective ability to detect and respond to emerging influenza threats,” she stated.
Outlook and Prevention
For the coming 2026-2027 season in the Northern Hemisphere, experts remain cautious about predicting severity. Dr. Daniel Jernigan, a former CDC director and contributing scholar at the Johns Hopkins Bloomberg School of Public Health, noted that “the only thing that’s predictable about influenza is it’s unpredictable.” While U.S. data for the week ending Sept. 12 showed minimal levels of influenza-like illness activity in all 50 states, cases are expected to rise in the coming weeks, with a typical peak occurring between December and February.
Scientists often look to the Southern Hemisphere for early indicators. Australia’s 2026 flu season has been moderate so far, significantly milder than its 2025 season, which was among the busiest and deadliest in decades. However, cases in Australia have been surging later than usual.
In the U.S., earlier this year, scientists updated the 2026-2027 flu shots specifically to protect against the H3N2 subclade K strain. Health officials continue to stress the importance of vaccination, particularly for high-risk populations, as most regions in Canada are set to offer shots to the general public by mid-October. While current data suggests a milder start in some areas due to H1N1 dominance, the potential for mutation and the lingering threat of H3N2 mean that prevention remains a critical public health priority.
