Ontario may be heading into a challenging flu season, with early surveillance data and global trends signaling a potential surge in infections. Public Health Ontario recently reported a noticeable increase in influenza activity during the final week of October, including three outbreaks, 14 hospitalizations, and 129 confirmed cases. The agency expects flu activity to continue climbing in the coming weeks, particularly among children.
Federal surveillance shows similar patterns nationwide. Roughly two per cent of flu tests across Canada were positive in the most recent reporting period, still below the threshold for declaring a full flu epidemic, but higher than earlier in the fall. Infectious disease experts say the situation in the southern hemisphere—where flu season occurs earlier—may offer insight into what Canadians can expect. Australia recorded one of its worst flu seasons in recent years, with a sharp rise in infections and low vaccination uptake, particularly among young children.
A major concern this year is the circulation of the H3N2 subtype of influenza A. While H1N1 has been the dominant strain for more than a decade, H3N2 is known to cause more severe illness, especially in infants, older adults, and people with weakened immune systems. Some early data suggests the current flu vaccine may be less effective against certain circulating versions of H3N2, though experts stress that vaccination remains the best defense. Even with potential strain mismatches, physicians emphasize that the flu shot significantly reduces the risk of infection and serious complications. “It’s still very much worth getting vaccinated,” said infectious disease specialist Dr. Isaac Bogoch, who noted that vaccines help prevent severe outcomes even when they do not completely block infection.
The severity of the flu season will depend on several factors, including which strain becomes dominant, how effectively the vaccine performs, and how widely people choose to get vaccinated. Other countries in the northern hemisphere, including England and Ireland, are already seeing early upticks in flu cases and hospitalizations. Health experts say now is the time for precaution. They recommend staying home when ill, maintaining good hand hygiene, and making flu vaccination a priority. The true extent of this year’s flu season in Ontario will likely become clearer by late December or early January.
