A surge of influenza among school-aged kids is linked to the recent deaths of multiple Ontario children, prompting calls for Canadian families to get vaccinated as medical experts brace for a worsening wave of infections across all age groups.
Three children between the ages of five and nine died from complications of influenza this month, health officials from Ottawa Public Health and the Eastern Ontario Health Unit said in a statement on Monday.
Officials aren’t releasing further information on the children, including whether or not they were vaccinated against flu or had any underlying health issues, but did note all three lived in the Ottawa area.
“Pediatric deaths due to influenza occur every year in Canada, but it is unusual to see this number of deaths over such a short period of time,” Dr. Trevor Arnason, Ottawa’s medical officer of health, told CBC News.
Across the country, the latest federal data shows more than 20 per cent of all influenza tests are now coming back positive, with the most detections among people aged 19 and under. (The same data suggests there have been fewer than five pediatric deaths country-wide so far this season, as of last week.)
The spike is driven by the spread of H3N2, which is typically linked to more serious flu seasons — including a recent subtype of H3N2 with mutations that don’t appear to cause more severe disease but make the virus quite distinct from those targeted in this year’s flu shot, according to the World Health Organization.
It’s been awhile since Canada experienced a flu season dominated by H3N2, noted Dr. Jesse Papenburg, a pediatrician and researcher at Montreal Children’s Hospital.
“So that means that there are a lot of kids who have not, maybe ever, been exposed to H3N2, and therefore there’s a lot of susceptibility to that type of infection in the pediatric population right now,” he added. “I think that’s part of what explains these really high positivity rates in kids.”
It also translates into a grim numbers game, Papenburg warned, as high circulation of flu among school-aged kids could mean more instances of serious outcomes — many of which could be prevented by annual flu shots, even if they’re not a perfect match to this year’s dominant strain.
The latest available vaccine effectiveness estimates show the current shot is up to 75 per cent effective at preventing hospital visits in children aged two to 17 years, and 30 to 40 per cent effective in adults, said the WHO.
“It’s not too late to get vaccinated,” Papenburg added.
While multiple regions are seeing a rise in kids with flu, the early and intense rise in illness among children and teens is playing out acutely in Ontario.
At CHEO, the Eastern Ontario children’s hospital located in Ottawa, more than 300 tests came back positive for influenza in the first 10 days of December, a striking spike compared to just 11 tests that came back positive during the same period last year.
Over the last week, the hospital’s emergency room has seen upwards of 220 to 280 visits per day, with up to a dozen daily admissions, hospital officials said.
The pediatric clinics at St. Michael’s Hospital and St. Joseph’s Health Centre in Toronto are also busy, with more tests coming back positive than the hospitals typically see at this time of year, said Unity Health Toronto pediatrician Dr. Anne Wormsbecker.
Children are coming in with a range of symptoms, including some patients with prolonged illnesses including fevers lasting multiple days, she said.
Province-wide, the percentage of influenza A tests coming back positive is now at roughly 26 per cent — higher than in any of the past three seasons, and with increases across all age groups, Public Health Ontario data shows.
Kids and teens are currently the hardest hit: Nearly 64 per cent of flu tests are now coming back positive among children aged five to 11, while more than half of flu tests are positive for those aged 12 to 19.
“That’s sky-high. That means the amount of influenza circulating among school-aged kids is really tremendous right now,” said Papenburg.
The handful of recent deaths in Ontario are a “tragedy,” he added, noting that in any given flu year, pediatric deaths can range from one or two to more than 10 over the course of the season.
B.C. Centre for Disease Control reports increase in flu cases among children
Papenburg was part of a team that analyzed pediatric flu mortality across Canada. That study identified 80 total influenza-associated deaths in Canadian pediatric hospitals between 2004 and 2022.
Their study, published in the Journal of Pediatrics last July, found children under five made up more than half of those cases, while those with high-risk conditions were close to 80 per cent of cases.
Only a quarter of hospitalized children with a known vaccination status had gotten the latest flu shot, the researchers found.
Medical experts expect it’s a similar situation this year, as public health teams stress that getting vaccinated against influenza is crucial while families begin gathering for the holidays.
“The sooner you get vaccinated, the better, because we know that during the holiday season, there’s going to be a lot of intergenerational mixing,” said Papenburg. “What I’m seeing down the road is that we might have a really bad influenza season for our most vulnerable population, which is our elderly.”
While flu often surges earliest among younger age groups, the eventual spillover into older adults typically leads to far more cases of serious illness. In recent weeks, federal data shows a rising number of influenza outbreaks in long-term care homes, for instance.
“We can help decrease the severity of symptoms, especially in those at a higher risk — so, the elderly, and young kids, those with chronic medical conditions,” said Dr. Sidd Thakore, a pediatrician at a children’s hospital in Calgary.
That facility is overcapacity largely thanks to an influx in young flu patients, he added, all while the hospital is also bracing for a rise in respiratory syncytial virus (RSV).
“[There’s] a lot of misinformation out there regarding vaccines,” Thakore said. “We’re seeing the result of that: We saw measles earlier, we’re going to see influenza now and then we’ll see what happens with RSV.”
In recent years, many vaccine-preventable illnesses, such as measles, have proliferated in countries like Canada as vaccination rates have dropped, despite significant evidence showing the safety and success of immunization programs in protecting people from serious disease.
Wormsbecker, in Toronto, recommended other basic precautions — including washing your hands, staying home when sick and not sharing food and drinks — alongside getting the seasonal flu vaccine.
“Just like in the summer, we wear sunscreen; it is not perfect … but it gives us some protection, and the vaccine does the same thing,” she said.
