- Throughout the pandemic, he explained, widespread COVID-19 infections may have kept people’s immune systems on high alert, giving SARS-CoV-2 a long-term advantage over the flu.
- Now, people talk about viral interference with influenza and COVID and I wouldn’t ignore anything.
- He is bracing for an uptick in the number of COVID-19 cases.
After long quiet, Influenza-A infections are on the rise in Canada, approaching the usual seasonal level as reported by CBC.
Family of viruses
For more than two years, as Canadians experienced a roller coaster of COVID-19 infections, influenza seemed to take a backseat.
The family of viruses that causes the flu was barely spreading across the country until a recent, belated return of Influenza A caught scientists’ attention.
In March — as COVID-19 restrictions lifted and more people began mingling — positive tests for influenza A viruses began rising in Canada.
By late April, federal data showed a nearly seven per cent test positivity rate, close to the average level for this time of year and largely driven by a spike in Quebec.
This unusually late flu season may offer clues for how COVID and influenza will impact each other in the years ahead, with one theory suggesting these two rival viruses could ebb and flow — but it’s tough to predict what, exactly, that would look like.
Flu typically spikes in winter
In a typical flu year, cases first rise in the fall, a spike in the winter and taper off in the spring, with sporadic infections throughout the rest of the year — with influenza A viruses circulating before influenza B. The viruses’ disappearance throughout the pandemic might be tied, in part, to shifts in behaviour throughout much of the last two years as COVID-19 surged unpredictably, variant after variant.
“We were able to successfully suppress influenza circulation with our other public measures related to COVID-19,” said Dr Danuta Skowronski, the epidemiology lead for influenza and emerging respiratory pathogens at the BC Centre for Disease Control.
The lifting of restrictions, coupled with a rise in global and domestic travel, likely played a role in influenza returning in recent months, said Dr Isaac Bogoch, an infectious diseases specialist at the University Health Network in Toronto.
A mismatched flu vaccine this season may be another factor behind this unusual spike, as U.S. public health authorities reported, or simply waning immunity from shots given back in the fall, according to Skowronski.
But some close COVID-19 watchers say the virus that causes it, SARS-CoV-2, may also have helped keep influenza at bay.
‘Viral interference’
There was once speculation that COVID-19 and flu could create what some dubbed a “twindemic,” with both types of infections hitting countries at once, but those fears haven’t materialized.
“There’s some type of interesting viral suppression and competition going on here,” said Chakrabarti, who suggested COVID and flu may ebb and flow in circulation.
Throughout the pandemic, he explained, widespread COVID-19 infections may have kept people’s immune systems on high alert, giving SARS-CoV-2 a long-term advantage over the flu.
“I think the short answer is you can’t get overconfident with how the next year or so is going to play out.”
“The circulation of SARS-CoV-2 — specifically Omicron — may have left people slightly immunocompromised,” she said.
Different patterns of influenza possible
Several experts who spoke to CBC News did agree there could be unexpected shifts in the influenza season based on how the virus behind COVID-19 operates going forward.
“Will SARS-CoV-2 and COVID-19 cases become more seasonal?
If so, we might see a different pattern of influenza cases,” Kelvin said.
In the short term — more reassuringly — both viruses are expected to fade away as the weather warms up before returning, at some point, in the fall.
“We’re going to have this upsurge again,” he warned.
The months ahead could be crucial to ensure Canadians continue getting vaccinations that offer protection against severe illnesses, while policymakers ensure there’s adequate space and staff to handle patients who do fall seriously ill with COVID-19 or flu.
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Source: CBC
