Canada is seeing an early rise in flu cases. Is a 'tidal wave' of infection coming?
CBC
Canada is on track to face its first full flu season in several years — one that's starting earlier than usual, all while the country's healthcare system is already grappling with respiratory infections like COVID-19 and RSV.
It's hard to know how the months ahead will play out, including what level of strain serious influenza infections will put on overrun hospitals, and how this year's slate of viruses will interact now that SARS-CoV-2 is firmly in the mix.
But what's clear is there's already a sharp rise in recent infections, and a "tidal wave" of cases is likely on the way, said Dr. Sameer Elsayed, an infectious diseases physician and medical microbiologist in London, Ont., and a professor with Western University.
"We're going to have a big influenza season, I expect, this year."
At the national level, influenza activity has been "increasing steeply" and crossed the seasonal threshold of five per cent of samples coming back positive by late October. Should those trends hold, the federal government will be declaring the start of an influenza epidemic in Canada in its next update, scheduled for Nov. 14.
Ontario has already soared past that benchmark, with roughly 10 per cent of tests recently coming back positive for this year's dominant strain of influenza A.
In the latest update from Public Health Ontario on Nov. 4, the province said the flu season has started "more than a month earlier than typically observed in pre-pandemic seasons."
That early start comes as the province's pediatric hospitals are already overflowing with children sick with illnesses including respiratory syncytial virus, or RSV, and while positive test results for COVID-19 are back on the rise, most recently hitting 17 per cent.
"In the coming months, Ontario will likely face the triple threat of respiratory illnesses," warned Dr. Rose Zacharias, president of the Ontario Medical Association, a physician advocacy group, during a press conference on Wednesday.
Alberta began experiencing a spike in influenza A cases as well by the end of October, alongside the circulation of other pathogens, and B.C. public health officials are also watching for an ongoing rise in positive samples.
"At the moment we are seeing influenza creeping up, and samples come in through long-term care facilities, children's hospitals, adult hospitals," said medical microbiologist Dr. Linda Hoang, the associate director and program head of the bacteriology and mycology lab at the B.C. Centre for Disease Control.
How Canada's flu season will progress from here could mirror, to some degree, what countries in the southern hemisphere experienced earlier this year.
In Chile, where the 2022 flu season has come and gone, influenza A began circulating "months earlier" than during pre-pandemic flu seasons, according to a recent report released by the U.S. Centers for Disease Control. (The U.S. is now experiencing an early start as well, with southern states seeing the largest surges.)
Chilean officials reported more than 1,000 hospitalizations during the season. That's higher than during the COVID pandemic when public health restrictions and other factors kept flu at bay for more than a year, but lower than during recent pre-pandemic flu seasons. The country's flu shots also cut the risk of hospitalization nearly in half.