It’s more than just a bad cold: influenza can also raise your risk of a heart attack shortly after an infection, medical experts are warning as the H3N2 strain spreads rapidly in Canada.
At the same time, flu season is coinciding with another risk factor for heart attacks – shovelling snow.
“Any time you get an infection, including a viral infection, there’s the release in your body of molecules that both trigger inflammation and sustain inflammation. And part of that is an increased tendency for your blood to clot,” said Dr. Fahad Razak, internal medicine physician at St. Michael’s Hospital and professor at the University of Toronto.
“That can have immediate effects within the weeks following an infection, resulting in things like strokes or heart attacks.”
Influenza brings with it an increased risk of heart attack and stroke, data shows.
People are four times as likely to have a heart attack and five times more likely to have a stroke in the month after laboratory-confirmed influenza, data published in the Journal of the American Heart Association in October shows.
The risk is also significantly higher following COVID-19 infections. People are three times more likely to have a heart attack and three times as likely to have a stroke in the 14 weeks following COVID-19 infection, with the risk remaining elevated for a year, that data shows.
A 2018 study published in the New England Journal of Medicine had previously found that the risk of a heart attack is highest in the first week following an influenza infection.
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“We saw that within the next seven days, there was a six times higher risk of having a heart attack compared to other times of the year,” said Dr. Jeff Kwong, one of the co-authors of the 2018 report and senior scientist at Toronto’s Institute for Clinical Evaluative Sciences.
The study found that there was a “clustering” of patients landing in the hospital from a heart attack in the first seven days after an influenza infection.
“That suggests it’s the influenza infection that’s triggering heart attacks,” Kwong said.
The higher risk of heart attacks underscores the need for older Canadians to get their flu shots as soon as they can, Razak said.
“This is an additional reason why people should be looking at getting their vaccinations up to date and reducing the risk of infection wherever possible using other measures like using a mask, not exposing people if you’re sick,” he said.
Kwong recommends moderation over the holidays if you’ve recently been sick.
“If you’re sick, then just stay in and see if you can get someone else to shovel the snow for you rather than go out there and try to tough it out. Because you know that’s two things that can trigger a heart attack happening at the same time,” Kwong said.
“You might not want to drink too much alcohol because that can also increase your risk for cardiovascular events. Maybe don’t eat too much because sometimes that can be a stressor on your body.”
For anyone worried about contracting the flu, vaccinations are your best bet, but having air filters at your holiday gatherings could provide an extra layer of protection, he added.
In the days following an influenza infection, any older person or person with a higher risk of heart disease should monitor symptoms like chest pain, shortness of breath, the sudden onset of weakness or fatigue or facial droop, Razak said.
“Things that would be suggestive of having that acute event. You should immediately seek medical attention,” he said.
“That would be my advice, of course, in general, any time of year, but be especially aware of those things if you are an older or high-risk individual and you’ve had one of these severe infections,” Razak added.
The rate of hospitalization from influenza in Canada has nearly doubled compared with the previous week of available data, with infections now up almost 30 per cent, Health Canada’s latest figures show.
For the week ending Dec. 13, Canada saw 11,646 new cases of flu being detected, which means 27.7 per cent of all the tests conducted in the country came out positive.
This was an increase of 71 per cent compared with the week before, which saw 6,799 new cases and a positivity rate of 20.2 per cent.
The flu is also landing more Canadians in the hospital, with hospitalizations at 6.2 people per 100,00 of population — up from 3.9 the week before.
The youngest and oldest Canadians are getting hit the hardest. The highest rate of weekly hospitalizations was in adults aged 65 years and over and children aged four years and younger.
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