Flu season didn’t really happen last year in Canada.
Measurements of flu stayed so low all year that it actually never passed the threshold the Public Health Agency of Canada normally uses to declare the start of the season — which usually happens in the fall.
PHAC recorded 69 influenza detections in the 2020-21 flu season, in its final FluWatch report on Aug. 28. Normally, around 52,000 cases are detected.
Flu had a quiet year because we were busy dealing with COVID-19, experts say. But what will happen this upcoming year is a little harder to say.
Usually, Canada can look to the Southern Hemisphere for clues as to what might happen here, said Dr. Gerald Evans, an infectious disease specialist at Queen’s University and Kingston Health Sciences Centre. Because their winter is during Canada’s summer, he said, it can provide a preview of what’s to come.
Australia is currently reporting “historically low levels” of influenza, according to a report on the government’s website. It’s not alone: the World Health Organization notes in a recent report that, “Globally, despite continued or even increased testing for influenza in some countries, influenza activity remained at lower levels than expected for this time of the year.”
This could be for two reasons, says Angela Crawley, a scientist at the Ottawa Hospital Research Institute and professor at the University of Ottawa. First, it’s possible that despite what the WHO report suggests, people in some countries just aren’t testing for, or reporting, flu infection like they used to.
“The pandemic closed us in and so people were not going to the doctor for their flu-like symptoms,” she said. And if they did go, they might have gotten a COVID-19 test and if it turned out negative, just been sent home, she added.
“They probably had the flu, possibly, but that wasn’t being tested,” Crawley said.
Second, she says, the measures used to contain COVID-19 probably contained the flu as well.
“The personal protective equipment, like the wearing of the masks and the significant effect of social distancing may have had (an effect) on the number or the prevalence of the virus in the community,” she said.
Flu this year
So what does this mean as Canada heads into the fall? Evans isn’t sure.
“The closest prediction I can get is that I think we’re going to see more numbers than we saw last year,” he said. “But that’s not a hard prediction to make since we saw record-low numbers last year.”
Continuing to wear masks and improved handwashing and other hygiene measures will probably “temper” this year’s flu season, he said, and lifting these measures could conversely, bring flu back.
International travel could have an impact too, Evans noted.
“Just recently, Canada allowed for fully vaccinated individuals from many countries around the world to come to Canada,” he said.
Normally, some flu gets brought to Canada by travelers from the Southern Hemisphere, he said, and this didn’t happen last year because of worldwide travel restrictions.
“Now that travel’s back up, maybe that will allow for that introduction, and we will see cases now because of the importation,” he added.
Crawley isn’t sure what will happen with the flu this year in Canada either, but she is sure that Canadians should still get their flu shot when it’s available.
“Immunologically, the body does not like to be infected by more than one thing at a time. And in fact, pathogens take advantage of this. So if you’re down and out with one infection, a co-infection is more likely to cause you significant disease,” she said.
Put another way, you don’t want to catch COVID-19 and the flu at the same time.
And more broadly, keeping flu numbers low can help ease the burden on emergency rooms while we’re dealing with the COVID-19 pandemic, Crawley added.
“If there’s ever any breakthroughs with COVID-19, which puts pressure on hospitalizations, if we were to also have a pressure of flu on top of that, it could be devastating to the health-care sector,” she said.