TORONTO (CNN) — Last winter, the flu was almost nonexistent due to lockdowns and public health measures aimed at cutting down COVID-19 cases, but experts are warning that this year, we may see a resurgence.

Traditionally, winter is the start of cold and flu season as people head inside to avoid the cold weather. Last year, the Public Health Agency of Canada (PHAC) only reported 79 lab-confirmed cases of influenza in its 2020-21 season, a fraction of the 54,000 cases logged the year before that.

But now, doctors across the country are reporting an increase in children and adults with colds and respiratory viruses.

“Without question, we are going to see influenza this year higher than we saw last year,” Dr. Gerald Evans, an infectious disease expert, told CTVNews.ca.

“Whether it’s going to be a sort of classic seasonal surge like we typically see or whether it’ll still be muted by the fact that we have a fair bit of public health measures still in many places in Canada, that’s the variable that we don’t know what impact that’s going to have.”

The minuscule amount of flu cases last year was a byproduct of all of the masking, physical distancing and lockdowns that were implemented to battle COVID-19. But with more than 87 per cent of the eligible population vaccinated, in some regions of the country, those public health measures have eased, causing doctors to wonder if the flu will make a comeback.

It’s hard to be sure. There isn’t much of the virus circulating right now

Dr. Donald Vinh, with McGill University Health Centre, told CTV News that there has been “significantly low flu activity in many countries, in many regions of the world — including the southern hemispheres, which is usually a harbinger of what we anticipate in the northern hemispheres.

“So some people interpret that as meaning that we may have a mild flu season in terms of the number of cases,” he said.

On the other hand, there is a concern that because there has been a lower amount of flu circulating since the start of the COVID-19 pandemic, this decreased exposure can lead to an outdated immune repertoire, where people may not have antibodies that are up to date to fight the current flu strains.

A preprint study published at the end of August, still awaiting formal review, predicted what it called a “large compensatory influenza season in 2021-22” due to a light season last winter.

Some are already seeing a sharp spike in colds and other respiratory viruses across the country. The worry is that influenza could follow.

“This could lead to more severe flu seasons, especially for those at risk in terms of hospitalizations and deaths,” Vinh said.

Already, the World Health Organization is reporting that while COVID-19 infections dominated most of 2020 and 2021, there is now a clear rise in influenza cases worldwide.

“We’re very much hoping that some of the reduction in influence we saw last year might have been because COVID was circulating at the same time,” Evans said. “But if that doesn’t happen this year, then we’re in for the infamous, what people like to call the ‘twindemic,’ which is two viruses causing a lot of cases, which can result in serious illness, and that would be very tough on the system to deal with.”

If flu cases were to rise at the same time as COVID-19, this could mean that COVID-19 and severely ill flu patients could be fighting for the same resources, such as ICU beds and ventilators this winter.

A study published this month from Australia called “The importance of influenza vaccination during the COVID-19 pandemic” noted that flu was picking up in some countries and could “pose a renewed threat in the upcoming Northern Hemisphere winter”, even though influenza circulation is currently low.

Co-authored by Dr Ian G. Barr, WHO Collaborating Centre for Reference and Research on Influenza, Melbourne, the study states that “viruses are still in circulation and can be rapidly transported when air travel returns leading to increased infections”, anticipating possible flu outbreaks later this year.

“Influenza vaccination […] should not be ignored,” said the report.

Research from the UK is also suggesting the two vaccines can be administered at the same time safely

And a study from University of Miami Miller School of Medicine, published in PLoS One this summer, found the flu vaccine may even provide added protection against severe outcomes if a person contracts COVID-19. Out of two cohorts of 37,000 people, those who had received an influenza vaccine had decreased sepsis and stroke associated with COVID-19, and had fewer emergency department visits.

Those in the study who caught COVID-19 and hadn’t had the flu shot were up to 20 per cent more likely to have been admitted to the ICU.

“Although it isn’t exactly known yet how the flu vaccine provides protection against COVID-19, most theories speculate that the flu shot may boost the innate immune system — general defences we are born with that do not protect against any one specific illness,” a press release on the study stated.

It’s important to note that the flu shot is in no way a replacement for a COVID-19 vaccine.

“It is safe to get your COVID shot, whether it’s your first or second dose, and your flu shot at the same time, irrespective of the timing of each,” Ajit Johal, a pharmacist and clinical director of Immunize.io, told CTV News.

Children as young as six months can get the flu shot, and measures like masking and staying home when sick — even with something other than COVID-19 — are critical this winter, experts say.

“If you have symptoms that might be of something contagious, COVID or not, please, please, don’t mingle with others, don’t go to work, don’t go to school, find a way to stay home until the symptoms are gone, because you’re going to wreak havoc,” Noah Ivers, family physician and Canada Research Chair at Women’s College Hospital and University of Toronto, told CTV News.

And as the weather cools, fall flu clinics will soon be opening across the country, as public health pushes every ounce of prevention going into another pandemic winter.

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