Skip to main content

New research suggests 'long flu' could have lasting impacts


As flu season sweeps across Canada and new research suggests the disease could come with a more long-term burden for some, health officials and experts are reminding the public of the importance of getting your shot.

It's been nearly three weeks since the start of flu season was officially declared in Canada and we're beginning to see cases surging in some regions, at the same time as COVID-19 cases are trending higher and higher.

Levels of influenza in Alberta right now are the highest they've been in 14 years. Data out of British Columbia is showing a rise in both influenza and respiratory syncytial virus (RSV). And the number of flu cases showing up in Manitoba hospitals is putting a strain on the health-care system, Manitoba Health Minister Uzoma Asagwara said Thursday.

Canada's Chief Public Health Officer, Dr. Theresa Tam, wrote in a statement Thursday that "respiratory illness season is well underway in Canada," and that influenza, RSV and COVID-19 are all circulating right now.

"If you haven't already done so, now is a good time to get your updated flu and COVID-19 vaccines."

John Papastergiou, a pharmacist based in Toronto, told in a phone interview that the flu shot shouldn't be an afterthought.

"Every year, the flu causes significant morbidity and even mortality to many Canadians," he said. "The most vulnerable, obviously, are the young and the very old, but really it can affect all of us. The only real way to combat it is to get vaccinated to protect our elderly – we protect our young family members – and obviously, to protect yourself."

He added that getting vaccinated as early as possible within the flu season is important in order to get ahead of the swell of cases, and that we'll be approaching that peak soon.


A study published Thursday in The Lancet Infectious Diseases suggests that influenza could create a long-term burden akin to long COVID on a less drastic scale.

The study looked at 81,000 patients in the U.S. hospitalized for COVID-19 between 2020 and 2022, as well as nearly 11,000 patients hospitalized for seasonal influenza at some point between 2015 and 2019, and tracked their progress up to 18 months post-infection.

"Five years ago, it wouldn't have occurred to me to examine the possibility of a 'long flu,'" Ziyad Al-Aly, a clinical epidemiologist at Washington University in St. Louis, Mo., and senior author of the study, said in a press release.

"A major lesson we learned from SARS-CoV-2 is that an infection that initially was thought to only cause brief illness also can lead to chronic disease."

The data confirmed that COVID-19 was significantly more deadly than the flu, with patients who had COVID-19 facing a 50 per cent higher risk of death, as well as a much larger risk of 64 different health conditions across all organ systems.

However, it also showed that the flu was capable of causing long-term damage that increased patients' risk of developing six different health conditions later in life, mostly in the respiratory system.

"The big answer is that both COVID-19 and the flu led to long-term health problems," Al-Aly said. "Long COVID is much more of a health problem than COVID, and long flu is much more of a health problem than the flu."

Papastergiou called the research "not surprising at all," stating that damage done during the acute phase of an illness makes the body more vulnerable to future illnesses.

"Once you've had a bad case of influenza, or COVID, we know definitively that puts you at risk for future cases," he said.

"I think it's not surprising when you have something like influenza, or pneumonia related to influenza, it's a massive inflammatory cascade, as well. And there's consequences to that down the line potentially – cardiovascular disease risk and everything else."

That's one of the reasons that vaccination is so important, he said.


Those at risk of developing a severe case of influenza tend to be the same groups at high risk for severe cases of COVID-19: those who are pregnant, have underlying health conditions, are immunosuppressed or are 65 years or older.

Young children are also at a high risk for serious cases of influenza, especially children aged six months to five years old, which is not the case with COVID-19.

The flu shot drastically reduces the likelihood of developing a severe case and ending up in hospital with influenza, Papastergiou said.

"This year, I'm seeing a little more hesitancy towards the flu shot than I have in previous years," he said.

"A lot of the myths now are 'I've already been vaccinated for COVID and flu in the past, I don't need it again this year,' (or) 'I've got too many vaccines over the last little while, that can't be good.'"

But the flu shot is different every year, optimized for whichever strain of influenza that researchers predict to be the most dominant based on Australia's flu season, which occurs before ours. And health experts recommend getting the flu shot every year, regardless of how recently you got a COVID-19 shot.

At Papastergiou's work at a Shopper's Drug Mart in Toronto, around half of their patients are receiving their COVID-19 booster shot and their flu shot during the same appointment, usually one in the right arm and one in the left.

"We're really recommending co-administration with the COVID booster, the newest version," he said.

It's perfectly safe to get both at the same time, but could leave you feeling a little more achy for the next 24 hours or so, he added.

Health Canada has authorized three XBB.1.5 vaccines, which are able to target newer variants of COVID-19, and the Public Health Agency of Canada (PHAC) is urging all Canadians to get their updated boosters amid increased COVID-19 activity this fall.


During the first year of the pandemic, influenza all but vanished in Canada — rates of flu were so low in 2020-21, with only 66 confirmed cases compared to the usual more than 43,000, that there technically was no actual flu season because cases never were high enough to reach the threshold to declare one.

This immense drop was connected largely to the public health measures that had been put in place to combat COVID-19, namely mask-wearing and physical distancing.

As health measures eased before vanishing completely, flu rates have gone back up. This year, Papastergiou is anticipating a larger flu season similar to pre-pandemic levels. He says those who are immunocompromised should definitely wear masks in settings where there's a lot of people in close contact.

"The benefits of the masks are well documented," he said. "They reduce the incidence of both flu, COVID and other respiratory illnesses."

PHAC is also recommending mask-wearing this flu season.

In her statement Thursday, Tam said that measures to reduce your risk of getting or spreading respiratory illnesses include "properly wearing a high quality, well-fitting respirator or mask in indoor public places, regular hand hygiene and improving indoor ventilation."

If you do come down with the flu, it's important to stay home if you're able in order to avoid passing it on to others. Over the counter cold medicine will also help to alleviate symptoms.

"If you've been vaccinated, it'll run its course faster," Papastergiou said, adding that while more vulnerable patients can receive oral therapies for influenza by prescription, none of them are a replacement for getting a flu shot.

Seniors who are on the lookout for a flu shot should know that although high-dose flu shots may be running low in some regions because they tend to go first, experts say getting a regular dose is better than holding out.

"As a senior, I wouldn't pass on vaccination in order to look for a high-dose vaccine," he said. "Get vaccinated early with whatever's available." Top Stories

Local Spotlight