The flu season of 2021 proved to be remarkably absent. By late April, Canada recorded a mere 72 instances of influenza, a stark contrast to the typical 50,000 cases seen in a standard year. This begs the question: what led to such a steep decline in flu cases, and what are the implications for the future?
A significant reduction in flu cases
Dr. Earl Brown, PhD, an emeritus virology professor at the University of Ottawa, remarked, “This is an unprecedented drop.”
According to Brown, while rhinoviruses—which are responsible for many cold cases—were still being reported, most other viruses that could infect the respiratory system were rarely seen.
It’s not just a Canadian phenomenon; many nations have experienced marked declines in flu cases, including a staggering 98% reduction in the United States.
This dramatic downturn coincides with the onset of the COVID-19 pandemic, leading many to speculate whether the two developments are connected.
The controversy over testing for flu and COVID-19
There are suspicions that flu infections may have been underreported due to overwhelmed testing facilities that prioritized COVID-19. In the U.S., the quantity of flu specimens submitted for testing plummeted by 61% during this period.
Conversely, Canada saw a significant increase in flu tests, nearly quadrupling the usual number, yet case counts remained stagnant.
Some contend that inaccuracies in testing protocols could lead to false positives for COVID-19 in patients actually suffering from influenza. In the U.S. and other countries, certain COVID-19 tests have had issues with reliability.
However, Canadian hospitals employed specific PCR tests specifically designed to detect COVID-19’s genetic material without misidentifying other viruses like influenza.
Dr. Gerald Evans, chair of infectious diseases at Queen’s University and former president of the Association of Medical Microbiology and Infectious Disease (AMMI) Canada, stresses, “It’s not accurate to claim that we missed flu cases simply because we were focused on COVID-19 testing here in Canada.”
He further elaborates, “We were actively searching for influenza and other circulating winter viruses, and we were concerned about a concurrent outbreak of COVID-19 and influenza. We identified numerous COVID-19 cases, yet found virtually none for influenza.”
Understanding the pandemic’s impact on flu transmission
The absence of flu cases seen recently is more about the impact of travel restrictions than the widespread use of hand sanitizer among the Canadian populace.
Evans clarifies that the flu virus relies on human movement to thrive and mutate, migrating from the southern hemisphere to the northern during winter. “The flu requires us to travel to spread into different regions of the world,” he notes. The pandemic drastically reduced travel, contributing to significantly lower flu numbers.
Moreover, once flu cases made it into Canada, local restrictions limited their capacity to spread. In fact, Canada’s flu surveillance program indicated “no evidence of flu circulating in the community” during the past season.
“Ultimately, all these factors led to only 72 reported flu cases in a year where we’d typically see tens of thousands,” Dr. Evans adds.
However, it’s important not to assume this means that flu and other respiratory viruses are gone for good.
Possible future ramifications of virus outbreaks
While social distancing, lockdowns, and travel restrictions have allowed us to avoid the latest flu season, these measures could lead to complications ahead.
“Emerging flu variants that may not be recognized by our immune systems are a concern,” warns Dr. Brown. “Resistance is key; if your immune system has seen previous flu strains, it can offer considerable protection. But if the virus evolves significantly, your immune response may not be effective.”
“Our flu immunity is likely to decline,” he adds. “This means we may become more vulnerable to respiratory infections we usually encounter. While it won’t be catastrophic, we can expect increased flu transmission.”
Looking to a new future
Dr. Evans notes, “Many of the precautions taken for COVID-19 have inadvertently shielded us from flu and other respiratory viruses. It remains to be seen how many of these practices we will continue.”
As you read this, travel bans may have been lifted, alongside many community restrictions. “People are fatigued,” Evans observes. “Many yearn for a return to normalcy, free from masks and anxiety.”
Nonetheless, he hopes folks will remain conscious of their health and take initiative to safeguard others when they’re feeling unwell.
“As someone focused on infection control, I’d be delighted if hand washing became routine,” he remarks with a chuckle. “Mask-wearing will be interesting; I envision some individuals choosing to wear masks in winter or when experiencing cold or flu symptoms.”
“If we can increase the number of people practicing these pandemic hygiene measures, benefiting overall public health, it will be an advantage for years,” asserts Evans. “There’s no doubt about that.”
