It was the flu season that never happened. By the end of April 2021, Canada reported only 72 influenza detections. In a typical year, that number would be closer to 50,000. Why did cases drop, and what does that mean for our future?
A dramatic decline in the flu
“We’ve never seen a dip like this,” says Dr. Earl Brown, PhD, emeritus professor of virology at the University of Ottawa.
“There were rhinovirus infections,” says Brown. Those are the viruses behind many cases of the common cold. “But many of the other 200 viruses that can infect your respiratory tract were essentially no shows.”
And it’s not just in Canada. Countries worldwide have seen a significant decline in flu activity, including a 98 percent drop in the United States.
This coincides with one major global change: the rise of the COVID-19 pandemic. Many people now wonder if it’s more than just a coincidence.
The flu price tag
Each case of the flu costs the Canadian health care system an average of $14,612 per person.
The debate surrounding COVID-19 tests and flu tests
Some people suspect that flu infections didn’t actually drop; rather they simply went underreported as overwhelmed labs and hospitals shifted their focus to the pandemic.
In some countries, that theory may hold some merit. For instance, the number of potential flu specimens submitted to be tested in the US dropped by 61 percent.
In Canada, things were the opposite. In the most recent flu season, Canada performed nearly four times the average number of flu tests. Yet flu cases still flatlined.
Others argue that testing protocols were inaccurate and that some COVID-19 tests can be “tricked” into thinking you have COVID-19 when really you have the flu.
It’s true that the US and many other countries authorized some types of COVID-19 tests that occasionally suffered from accuracy problems.
But in Canada, our hospitals and laboratories use a specific polymerase chain reaction (PCR) test that looks for the specific genetic material of COVID-19 and doesn’t falsely flag the influenza virus.
“The idea that we were only testing for COVID-19 and so we missed all these flu cases—at least here in Canada—that’s just not a reason,” says Dr. Gerald Evans, the chair of infectious diseases at Queen’s University and the former president of the Association of Medical Microbiology and Infectious Disease (AMMI) Canada.
“We were looking for influenza and other viruses that circulate in the wintertime,” he adds. “We were very worried that there was going to be a double hit of COVID-19 plus influenza at the same time. We found lots of COVID-19, but we just didn’t find influenza.”
The real reason the pandemic eliminated the flu
The no-show status of the past flu season has less to do with Canadians stockpiling hand sanitizer, and more to do with airplanes.
Evans explains that the influenza virus needs to move through the globe from host to host in order to mutate and survive, with the annual flu season first beginning during the southern hemisphere’s winter season before migrating through the northern hemisphere during our winter season.
“The flu needs us to travel to be able to introduce itself to a different part of the planet,” he explains. “And the pandemic significantly curtailed travel, so the numbers we started with were dramatically low.”
Once some cases of the flu did arrive, our local pandemic travel restrictions and community closures prevented it from spreading further. In fact, Canada’s national flu surveillance program reported that there was “no evidence of community circulation of flu” in the past flu season.
“All of that contributed to  cases of the flu in a season when we would normally have tens of thousands of cases,” says Dr. Evans.
But don’t hold your breath if you’re hoping that this means the flu and other respiratory viruses have been wiped out.
Revenge of the virus
Social distancing, staying home during lockdowns, and pushing pause on those vacations abroad have helped us dodge the most recent flu season. That in itself could create future problems.
“We’ve got new flu variants around the planet that look different to your immune system,” warns Brown. “That’s the key to resistance. If your immune system sees previous viruses, it’ll protect you pretty well. But if [the] too much, your immune system might not stop it.
“Our immunity to the flu will go down,” Brown says. “We will be more susceptible to all respiratory infections we’re normally exposed to. It’s not going to be cataclysmic, but numerically, it will mean we will see more flu transmission.”
A new status quo
“A lot of the things we do for COVID-19 have protected us from the flu and other respiratory viruses,” says Evans. “The question will be how much of this is going to be maintained.”
By the time you’re reading this, travel restrictions might be fully lifted, as will many other community restrictions. “People are tired of it,” says Evans. “People would love to walk around without a mask and not worry about things so much.”
However, Evans hopes that people will be more aware of their own health and take steps to protect others if they feel under the weather.
“As an infection control and infectious disease specialist, I’d be thrilled if I could get way more people to wash their hands,” he laughs. “Mask wearing is going to be interesting. I think we are going to see some people wearing masks in the winter, or if they have cold or flu symptoms.
“If we can get an increasing percentage of the population to adopt some of these things we did during the pandemic, just to keep yourself generally hygienic as a precaution, that is going to be a benefit for years to come,” says Evans. “There’s no question about it.”
The cold facts about respiratory diseases
We take the flu and common cold for granted today, but understanding of these viruses happened relatively recently.
An ancient problem
The world’s first documented influenza pandemic occurred in 1580. However, one of the earliest written records of what sounds like the flu is dated to 412 BCE. Meanwhile, COVID-19 may be new, but some researchers think a similar coronavirus pandemic swept Asia and then went global in the late 1800s.
A recent discovery
The influenza virus wasn’t identified until the 1930s. And the rhinovirus, which causes many colds, wasn’t discovered until 1956.
The viral dance
“There’s this dance as respiratory viruses compete for our lungs,” says Dr. Earl Brown, PhD, emeritus professor of virology at the University of Ottawa. “Certain rhinoviruses will trump coronavirus infections. If you get a rhinovirus, it will help stop the coronavirus from replicating in your respiratory system. A lot of other viruses get blocked by rhinoviruses too, so there’s this push and pull. The dance will go on.”
Your natural immunity
Researchers have found that your immune system naturally makes anti-flu antibodies, but levels can vary from person to person. Support your immune system with natural supplements and healthy lifestyle choices including
- getting enough sleep
- staying hydrated (try herbal tea with manuka honey)
- taking supplements such as vitamin C, quercetin, elderberry, and vitamin D