Flu circulating at 'sky-high' levels among kids, teens as experts brace for worsening wave of infections

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.