Many more children are being admitted to hospitals with influenza than at any other time in at least a decade, according to surveillance data that show how an aggressive early start to the flu season is straining Canadian pediatric hospitals that were already near a breaking point.

In the last full week of November, there were 223 children admitted for influenza-related illness to 12 pediatric hospitals that are part of IMPACT, a network that tracks vaccine-preventable diseases in children. That’s considerably more than in any other week in years. Normally, there would be an average of 11 such hospital admissions a week at this time of year.

“Our flu season has just exploded,” said Jesse Papenburg, a pediatric infectious-disease specialist at Montreal Children’s Hospital and a data captain for IMPACT. “Last season – the entire influenza season – we had roughly 400 hospitalizations. That gives you a sense of the intensity of the activity, at least in terms of severe disease in children.”

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The soaring number of flu cases is having a cascading effect on a pediatric health system that was already struggling with pandemic-related staffing shortfalls and a surge of respiratory syncytial virus, or RSV, a virus that front-line experts said is now plateauing in Canada.

This week, a small team from the Red Cross will shore up staffing at the Children’s Hospital of Eastern Ontario (CHEO), an overburdened Ottawa pediatric hospital, while a Calgary children’s hospital will close respite beds for medically complex but stable children so nurses can be redeployed to care for the acutely ill. The only pediatric hospital in Newfoundland and Labrador, meanwhile, will join the growing ranks of children’s hospitals scaling back surgeries to free up staff for children in respiratory distress.

The 2022-2023 flu season, “just came out of the gates really intensely,” said Lynora Saxinger, an infectious-disease physician at the University of Alberta in Edmonton. “It’s creating a fair amount of havoc, honestly.”

She added that RSV, which continues to pose challenges to pediatric hospitals, appears to have levelled off, while COVID-19 is less of a factor in hospital admissions for children than it is for the elderly. “It’s been pretty stable for kids,” Dr. Saxinger said. “COVID is not a humongous player compared to influenza.”

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Influenza season normally begins in the fall and peaks in January or February. COVID-19 and the measures used to control it, including shutdowns, physical distancing and masking, kept the flu at bay from March of 2020 until last spring, when there was a small surge as restrictions eased.

Now the flu is back with a vengeance, particularly in Alberta, where flu activity is already “widespread” across the province, according to the Public Health Agency of Canada’s most recent FluWatch report, which covers the week of Nov. 20 to 26.

Alberta Children’s Hospital is responding to the strain by temporarily closing respite beds at Rotary Flames House, an affiliated hospice across the street from the Calgary hospital. The respite service provides a one-week break for families of children with complex medical conditions who require round-the-clock care.

The nurses and other health workers who care for those children will be moved to the hospital to staff six new short-stay beds for children in respiratory distress. The palliative, end-of-life and grief services normally offered at the hospice will continue to be offered inside the hospital.

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Suspending respite services until the flu and other viruses subside, ”was a very difficult decision for us,” said Margaret Fullerton, a registered nurse and the senior operating officer at Alberta Children’s. “We really are very empathetic with families because we know that they count on this.”

In Ottawa, CHEO, which has already opened a second pediatric ICU to deal with the extraordinary viral season, has called in a small contingent from the Red Cross to support its clinical teams, beginning this week, said Tammy DiGiovanni, senior vice-president and chief nursing executive at CHEO.

“This will allow some of our redeployed staff to go back to their regular roles and ensure Team CHEO can provide the safe, world-class care that our patients deserve,” she said in a statement.

So far this flu season, there have been 707 hospital admissions related to pediatric influenza, 95 ICU admissions and fewer than five deaths, according to IMPACT figures included in the Public Health Agency’s FluWatch report. (As a general rule, PHAC declines to release precise data if fewer than five patients are involved, citing privacy concerns.)

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The vast majority of cases in Canada are being caused by H3N2, a strain of influenza A. Although it is too early to properly judge the effectiveness of this season’s flu shot, Dr. Papenburg said that sequencing of the strain’s genetic code coupled with lab studies suggest it is a “really good match for the vaccine.”

Unfortunately, he said, too few children have received flu shots. He said families were likely caught off guard by the abnormally early start to influenza season, while others may not have been thinking about a virus that barely circulated during the first two years of the pandemic.

Vaccination is “one thing that families can do to help reduce the risk of having severe influenza infection now that we’re seeing so much of it circulating,” Dr. Papenburg said.