The anticipated flu season did not materialize. By late April 2021, Canada recorded just 72 instances of influenza—far below the usual figure of around 50,000 for a typical year. What led to this remarkable drop in cases, and what does it indicate for our future?
A striking decrease in flu activity
“We’ve never encountered such a low incidence,” remarks Dr. Earl Brown, PhD, emeritus professor of virology at the University of Ottawa.
“While rhinovirus cases persisted,” Brown adds, referring to the viruses responsible for many common colds, “most of the other 200 respiratory tract viruses were notably absent.”
This trend isn’t unique to Canada; nations around the globe have reported significant drops in flu cases, evidenced by a staggering 98 percent reduction in the United States.
This coincides with a significant global change: the emergence of the COVID-19 pandemic. Many are left questioning whether there is more than mere coincidence at play.
COVID-19 Testing vs. Flu Testing: The Ongoing Debate
There are speculations that flu infections did not genuinely decline; instead, they were likely underreported as laboratories and hospitals refocused their efforts on COVID-19.
In certain nations, this theory might hold some validity. For example, the volume of flu specimens submitted for testing in the US dropped by 61 percent.
Conversely, Canada saw a surge in flu testing, nearly quadrupling the average from previous seasons, yet cases still remained stagnant.
Some contend that testing protocols were flawed, suggesting that certain COVID-19 tests could misidentify flu infections as COVID-19.
While it’s true that many countries, including the US, authorized some COVID-19 tests that faced accuracy challenges, Canada employed a distinct polymerase chain reaction (PCR) test specifically designed to detect the genetic material of COVID-19 without misclassifying influenza.
“The notion that we were exclusively testing for COVID-19 and inadvertently neglecting flu cases—at least in Canada—just doesn’t hold,” asserts Dr. Gerald Evans, chair of infectious diseases at Queen’s University and former president of AMMI Canada.
“We actively sought out influenza and other respiratory viruses that typically circulate in colder months,” he adds, noting concerns over a potential dual threat from COVID-19 and influenza. “While cases of COVID-19 were prevalent, influenza remained elusive.”
Understanding the Pandemic’s Impact on Influenza
The absence of flu cases during the recent season is more related to reduced global travel than to Canadians stockpiling hand sanitizer.
Evans notes that the influenza virus relies on human travel to spread and evolve, typically migrating from the Southern Hemisphere during their winter to the Northern Hemisphere during our colder months.
“The flu thrives on human movement to establish itself in different regions of the world,” he explains. “The pandemic drastically limited travel, resulting in a significantly diminished starting point for flu outbreaks.”
As the rare flu cases emerged, stringent local measures and community shutdowns curtailed their further propagation. Canada’s flu surveillance network even indicated a total absence of flu community circulation this past season.
“All these factors contributed to the mere 72 flu cases in a season that would typically see tens of thousands,” Dr. Evans elaborates.
However, don’t expect a permanent reduction in the flu and other respiratory viruses.
The Potential Return of Respiratory Illnesses
Measures such as social distancing, lockdowns, and travel restrictions helped us evade the last flu season, but these changes might precipitate future challenges.
“New flu variants emerging globally will seem unfamiliar to our immune systems,” warns Brown. “Familiarity with prior strains generates resistance. If [a new variant is] too divergent, however, our immune defenses might falter.”
“Our flu immunity will diminish,” Brown cautions. “As a result, we may become more vulnerable to respiratory infections we usually encounter. Although it’s not likely to be catastrophic, we could witness an uptick in flu incidents.”
Adapting to a New Normal
“Much of what we implemented for COVID-19 has inadvertently shielded us from flu and other respiratory viruses,” notes Evans. “The pertinent question is how many of these measures will endure.”
When you read this, many travel restrictions may have been lifted, along with various community measures. “People are weary of restrictions,” Evans observes. “There’s a strong desire to move about freely without masks or constant anxiety.”
Nonetheless, he hopes individuals will remain vigilant regarding their health and take proactive steps to prevent spreading illnesses when feeling unwell.
“As someone focused on infection control, I would be delighted if more individuals adopted routine handwashing,” he chuckles. “Wearing masks could become common in the winter, especially for those exhibiting cold or flu symptoms.”
“Should a larger swath of the population adopt practices from the pandemic, it could foster a culture of health-consciousness that benefits us in years to come,” says Evans confidently. “This is undoubtedly positive.”
