The H3N2 strain of the influenza virus is spreading rapidly in the United States, with one in three flu tests coming back positive in the latest data that includes the holiday period.
Experts are warning that this could be a sign of things to come for the flu season in Canada, with new federal data set to be released for this country on Friday.
The U.S. Centers for Disease Control and Prevention (CDC) said around one in three (32.9 per cent) of influenza tests came back positive for the week ending Dec. 27.
“The most frequently reported influenza viruses this week were influenza A(H3N2),” the CDC said.
The data indicates a holiday spike, since the positivity rate was up from 25.6 per cent for the week ending Dec. 20, 2025. Around a month ago (the week ending Nov. 29), the positivity rate was 7.1 per cent.
More Americans landed in hospital because of the flu over the holidays, with the hospitalization rate at 31.3 per 100,000 of population – up from 22.9 the week before.
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The flu landed 33,301 Americans in hospital for that week, compared with 19,035 the week before.
Nearly one per cent (0.9 per cent) of all deaths reported in the U.S. that week were attributed to influenza, including the death of a child.
The dominant strain in the U.S. and Canada this year is called H3N2 subclade K.
Canadians should be cautious in the weeks coming out of the holidays, said Dr. Fahad Razak, internal medicine physician at St. Michael’s Hospital and professor at the University of Toronto.
“We have data that is very suggestive that we’re having an incredibly bad flu season here in Canada as well,” he told Global News last week.
“We can look to other countries, the experience in parts of Europe, now the United States and before that in Australia and Japan suggested some of the worst, or the worst, flu seasons on record.”
The rate of hospitalization from influenza in Canada has nearly doubled compared with the previous week of available data, with infections now up almost 30 per cent, Health Canada’s latest figures show.
For the week ending Dec. 13, Canada saw 11,646 new cases of flu detected, which means 27.7 per cent of all tests conducted in the country came out positive.
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