We're close to cold and flu season. So, what does that look like with COVID-19 in the mix?

For several years, pandemic restrictions and social distancing helped keep a variety of respiratory viruses at bay, even as rates of COVID-19 ebbed and flowed. Influenza largely disappeared until early 2022. Respiratory syncytial virus (RSV) infection rates were close to zero for months.

Now, we're entering uncharted territory.

Most restrictions are lifted, global travel has bounced back, and mandates for masks and boosters are few and far between. This fall and winter, with society largelyreopened, scientists say they suspect we'll experience the return of cold and flu season this time around, with another respiratory pathogen in the mix.

But how exactly the months ahead will play out is tough to predict.

"I think to be perfectly honest, nobody really has a good understanding of what the fall is going to look like," said Dr. Michael Gardam, an infectious diseases specialist and CEO of PEI Health.

Experts note avariety of scenarios are possible. Pathogens like SARS-CoV-2, influenzaand RSVmight take turns hitting the public. Perhaps we'll see COVID-19 and flu infections rising in lockstep dubbed a "twindemic" by some scientists. Or there's a chance it'll just be the flu coming back with a vengeance, as other viruses take a backseat.

Any of those three possibilities could be difficult for individuals to navigate, and each is capable of putting serious strain on Canada's already-struggling health-care system.

"If I had to guess, I'd say we might have a moderately bad flu year," Gardam said. "COVID I have no idea."

Early clues from Australia's flu season

While there's no crystal ball to tell us exactly what's ahead, Australia's 2022 influenza season does offer some clues. There, the seasons are flipped from what people experience in North America, which typically offers an indication of what's to come in Canada.

Earlier this year marked Australia's first big COVID-19 surge of the pandemic, with subsequent waves of rising and falling daily infections playing out like a rollercoaster all the way into late summer.

The country also endured its worst flu season in recent years, and data from Australia's Department of Health and Aged Care show infections were higher than the five-year average with infections notably spiking, then dropping, earlier than usual.

"Australia is having a real challenge [with flu] but we know at the same they're having a challenge with a lot of COVID," said Gardam, "and so it's just hard to tease out what's what."

It's possible that the country's recent flu season was an example of the influenza virus taking turns with SARS-CoV-2, said Alyson Kelvin, a virologist and researcher with the Vaccine and Infectious Disease Organization at the University of Saskatchewan.

"But we'll have to see a couple seasons of winter virus circulation to know that a bit better."

Viruses known for causing the common cold tend to circulate at different times than influenza, she continued, while COVID has popped up during the winter, at times when flu would normally circulate in Canada.

"That's the concern: What will those two viruses do when they circulate around the same time?" Kelvin questioned.

Expecting a 'really busy flu season'

Dr. Allison McGeer, an infectious diseases specialist with the Sinai Health System in Toronto, is among those bracing for that possibility.

"If we were just looking at COVID going into the fall, I think that would kind of be OK," she said. "The problem is that what we're expecting on top of it is a really busy flu season."

But there's also a chance this year will just be marked by the return of the flu, not a major COVID surge, Gardam said.

More socializing indoors, or the arrival of yet another more-contagious or immune-evasive variant could certainly push case COVID counts up. At the same time, Gardam noted that Canada did already experience a wave late this summer, thanks to the rapid spread of BA.5, the latest Omicron subvariant to take hold.

"If we don't see another variant show up, those of us who've gotten infected with COVID and been vaccinated, we're pretty good for the next few months," he continued. "So maybe the fall will be quiet."

WATCH | Why it took so long for flu to return in Canada:

Unusually late flu season hits Canada

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Experts believe lifting public health restrictions may be to blame for an uptick in flu cases across the country, adding pressure to hospitals already under strain from the pandemics sixth wave.

Pandemic precautions still have a purpose

A calm fall overall would be an ideal scenario, given the problems already plaguing Canada's health-care system, from family physician shortages, to long wait times at emergency departments, to high levels of hospital patients who are stuck waiting for alternatives like home or long-term care. But experts say it's also unlikely.

"The combination of the state our health-care system is in, the fact that we're going to continue to have COVID, the fact that we want to be catching up on all of the surgeries and other things that we got behind on and the busy flu season is going to make it really hard," McGeer warned.

The scientists and medical experts CBC News spoke to agreed that there will be some level of circulation of multiple viruses, potentially overlapping at different points in the fall and winter.

At a minimum, that could be disruptive to individuals' lives, and cause absenteeism across a wide variety of sectors including within healthcare itself. It also makes it harder to know which virus you've got, with so much similarity between cold, flu and COVID symptoms.

"It's a little bit different now expecting people to be able to kind of interpret their situation, and do what is right for them, than it was three years ago," McGeer said.

Even so, she said time-tested pandemic protections do still apply, including staying up-to-date on vaccinations, isolating when sick, and taking a COVID test.

On the prevention side, it's worth getting both an annual flu shot and a COVID booster, several experts agreed. In particular, bivalent COVID vaccines that are expected to arrive this fall for adults which target both the original SARS-CoV-2 and members of the Omicron family may recover some protection vaccines offered a year ago, which was later lost as new variants learned how to better evade our immune systems, Gardam said.

If you do catch a bug and aren't sure what it is, McGeer said it's worth taking time off work, if possible, and taking a COVID test.

"Rapid tests are really useful for figuring out what your symptoms are due to, and what you need to be doing," she added.

Then, barring any changes to government policies this fall, it'll be up to individuals to figure out their next steps.

When to isolate

Health-care workers in close contact with patients should continue to isolate at home if possible, regardless of their test results, McGeer said, along with anyone who does get a positive result for COVID.

People in any roles who test negative should still consider themselves contagious with some kind of virus and take steps to mitigate transmission, which could mean skipping social events, working from home, and wearing a mask if you work alone in an office or while running essential errands.

Those pandemic principles are worth carrying forward, Kelvin said, since COVID isn't the only pathogen that can take a toll.

WATCH | WHO reportsmore than 1 million COVID deaths in 2022 so far:

More than 1 million dead from COVID-19 so far in 2022: WHO

2 years ago

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WHO COVID-19 technical lead Maria Van Kerkhove said it was 'concerning' and 'tragic' that more than 1 million people died from COVID-19 this year. She expects more hospitalizations and more deaths as the virus circulates around the world.

"Influenza is a serious disease so if you have symptoms that look like influenza, that can also be confused with COVID-19, you should isolate yourself."

If Canada faces a challenging fall and winter, and infections from multiple pathogens begin putting a serious burden on the health-care system, Gardam said it would be worth returning to widespread public health measures.

"If it looks like we're getting into trouble, I personally would be recommending asking people to mask indoors," he said.

"That's not remotely a lockdown right? I don't think anybody ever wants to go back to a lockdown again, but simple things like wearing a mask, frankly, I don't think it's that big a deal."