Commonwealth_ This is shaping up to be what health officials and medical experts say will be an especially rough flu season, with influenza cases spiking across the country. The spike is due to the global and far-flung distribution of this ever-changing H3N2 variant of influenza, which may not match this year’s vaccine, thus raising the potential for more illness and severe cases.
Recent federal data suggests that about two percent of tests across the country came back positive for influenza last week. That’s still below the five-percent threshold for Canada to declare a seasonal flu epidemic, but notably higher than previous weeks. The upward trend could mean the country is edging into a period of heightened flu activity—at least as winter nears.
Observations from the Southern Hemisphere and other parts of the world detail a concerning pattern: countries in the Southern Hemisphere saw record-high case counts, and parts of Asia and the UK have seen an unusually early start to their flu seasons. International trends like these are often a bellwether for what Canada may face in the coming months.
It has been one of the worst influenza seasons in ten years, with high infection rates and heavy pressure on health services. Experts said it could be just as severe this year if the H3N2 strain currently circulating worldwide continues to gain ground. The virus has already demonstrated an early and intense activity pattern. The United Kingdom reported that this year’s flu season began more than a month earlier than usual, with three times the cases seen last year. In Japan—where the flu epidemic was declared—many schools have had to close. The new concern is the H3N2 subtype of influenza A. That’s a type that usually causes more serious disease, especially among older adults, and has changed significantly recently, possibly making this year’s vaccine less effective.
Generally speaking, the H3N2 subtype had usually been relatively stable over the past years. However, since the virus spread to the northern countries, the circulating strain has gotten increasingly different from what’s in the seasonal flu shot. Currently, the influenza vaccine in use in Canada includes two types of influenza A: H1N1 and H3N2, and one type of influenza B. Changes to H3N2 have pushed the virus further away from the vaccine, which might impact how well the vaccine protects against it. Health authorities caution that the severity of a given influenza season is impossible to predict accurately because of the inherently unpredictable nature of the virus.
Influenza is among the most mutable viruses; the large potential for change creates mismatches between circulating strains and formulations selected for vaccines. Yet, understanding trends across the globe and early data nationally are an indication that this year may be an active flu season, and health professionals must prepare themselves and the public accordingly. These measures include getting the seasonal flu shot, frequent hand hygiene, avoiding close contact with ill people, and staying home when sick, among others, to protect against flu infection.
The public health officials continue to monitor the situation closely and remind Canadians to continue showing vigilance for the rest of winter. Influenza is already showing early signs of activity internationally, with cases on the rise in Canada, which could lead to a particularly challenging flu season in the coming months. Health experts continue to closely monitor the evolving H3N2 strain and its potential impact on Canadian populations, adjusting public health guidance as necessary to minimize illness and protect vulnerable communities.
