COVID, RSV, flu: Will Canadians face a tripledemic this fall? Experts weigh in

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As fall approaches, Canadian health care staff are preparing for a busy flu season — though the influenza virus isn't the only one making the rounds.

According to an infectious disease specialist, it's still difficult to predict exactly how bad influenza will be throughout the fall and winter.

"It's predictably unpredictable," said Dr. Isaac Bogoch. The expert, working at Toronto General Hospital, explained there are some patterns health officials look at to prepare.

"What we can do is look to the southern hemisphere because that often gives us a clue as to what we may expect in our flu year."

So far, Bogoch said the southern hemisphere seems to have a regular flu year, which means it's not worse than what would be expected.

The doctor is hoping for the best, and said there are ways Canadians can help.

"Hopefully we have a mild flu season, but we need more than hope. I think it's very important when the flu vaccines are available that people go out and get one."

Influenza: What to expect

The flu, a contagious infection of the nose, throat and lungs, is caused by influenza A and B viruses.

Each year in Canada, about five to 10 per cent of adults and 20 to 30 per cent of children are infected with influenza.

According to Health Canada, flu symptoms can include:

• Sudden fever and chills

• Coughing and sore throat

• Headache and muscle aches

• Loss of appetite and fatigue

Most people will recover within a week to ten days, according to the agency, but some people may experience health complications due to the virus. Those can include pneumonia, sinus infections or worsening of chronic medical conditions, such as heart disease, asthma and diabetes.

Though Bogoch said it's difficult to predict what influenza infection numbers will look like, each year in Canada around 12,200 people are hospitalized and 3,500 die due to influenza and related complications.

The flu season across the country normally runs from November to April, but it won't be the only virus around during that time.

Other viruses circulating

Bogoch claimed it's not just the flu that people need to worry about as fall rolls around.

There will also be a rise of RSV and COVID-19 cases, once again.

When it comes to COVID-19, the doctor explained infections are still popping up as the Omicron subvariant, EG.5 or Eris, becomes the dominant strain globally, including Canada.

In addition to the coronavirus, Canadian health officials also predict a rise in respiratory syncytial virus (RSV) infections.

RSV is a major cause of lower respiratory illness, particularly among infants, young children and older adults, Health Canada stated.

In Canada, RSV causes yearly outbreaks of respiratory tract disease, usually starting in the late fall through early spring.

The virus causes coughing, runny nose, fever and a decrease in appetite and energy in those infected. It can also sometimes cause severe infection of the lower respiratory tract, which can only be managed in the hospital. Infants frequently have bronchiolitis, which presents as wheezing and increased work of breathing.

"RSV is thought of mistakenly as an infection of childhood, but it certainly isn't ... it can infect anyone," Bogoch said.

"In fact, in the hospital, most people with RSV infections are in the adult hospitals. They're people typically on the older end of the spectrum or people with underlying health conditions that put them at greater risk."

There are also viruses that cause traditional colds, called rhinoviruses and enteroviruses, circulating in Canada.

What vaccines you need this fall

Here's what vaccines will be made available this fall:

• Influenza vaccine, also known as the flu shot

• New COVID-19 vaccine

• RSV vaccine for eligible adults over 60

As the Government of Canada puts it, vaccination works by exposing the body to "key parts of bacteria or viruses, called antigens."

"Later, if we are exposed to that same bacterium or virus, our immune system will be able to recognize the antigen and respond more quickly to help prevent us from getting the disease or from getting seriously ill," the government stated.

Bogoch said though "vaccines aren't perfect," they can reduce the chances of severe illness.

"It's especially important for people at greatest risk for severe infection to get the vaccination," he said.

Those at-risk include people who:

• Are 65 years of age and older

• Live in long-term care facilities or nursing homes

• Have underlying medical conditions, including diabetes and lung and heart diseases

Bogoch's advice is to get the influenza vaccine early on in the fall season.

Earlier this week, Health Canada approved Moderna's updated COVID-19 vaccine. Officials are notably not calling them booster doses, since these new vaccines are like the annual flu shot.

For COVID-19 booster doses, Health Canada stated NACI has previously "recommended that at least one booster dose should be offered to all adults 18 years of age and over, and adolescents 12 to 17 years of age who are at increased risk of severe illness, along with additional specific population recommendations in the fall of 2022 and spring of 2023."

In early August, Health Canada also approved the first RSV vaccine for adults 60 years of age and older, which Bogoch called "amazing, as it's been decades in the making."

Will Canada go through a tripledemic?

While Canada saw a rise of RSV, flu and COVID-19 cases last fall, it's unknown whether another tripledemic will occur this year.

"The reality is that it's really hard to predict the future ... because it's not whether or not there will be those viruses because it's clear they are still circulating," said Dr. Donald Vinh, an infectious diseases specialist at McGill University Health Centre, who added it's question if they'll occur at the same time.

"RSV and the flu season occur between September to December, and if we throw on top of that COVID, then we can get triple damage," said Vinh.

However, he added that his main concern isn't necessarily if these three viruses occur at the same time.

"My concern is, really, the potential for three viruses to prolong the demand on the health care system over a long period of time, over weeks if not a few months, which may be too much."

How can vaccines help avoid a tripledemic?

Vinh said one of the reasons why Canada may have had such a bad flu, COVID and RSV season last year is because people didn't have proper immunity.

This doesn't mean, however, that being exposed to a virus will help protect someone from getting sick.

"If you had RSV last year or the year before, ... it doesn't necessarily mean that you'll be protected the third or fourth time from severe illness. That's a bit of a gamble," he said.

Vinh said the way to get effective immunity is through vaccines, which will help avoid a tripledemic from happening on an intense scale.

"We know, for example, that the influenza vaccine was very effective, at least offering 52 per cent protection against severe or life-threatening disease and then, of course, the effectiveness goes up in more high-risk groups," said Vinh.

"The RSV vaccine will allow people to acquire immunity without being infected and getting severely ill."

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