Five times more risk of stroke: researchers warn of the little-known dangers of the flu

The flu doesn't just affect the lungs, it also significantly increases the risk of developing cardiovascular problems.

A little-known but very real risk. The flu is certainly dangerous for the lungs, but it is also dangerous for the heart. "We have known for many years that the flu can increase the risk of major adverse cardiovascular events," warned Professor Thomas F. Lüscher, president of the European Society of Cardiology, in a statement published in June 2025. A major study has recently reviewed these risks caused by the flu.

Published on October 29, 2025, in the prestigious Journal of the American Heart Association , the study confirms the alarming link between the flu and cardiovascular risk. "In the weeks following a bout of the flu, the risk of heart attack or stroke can increase dramatically," the American Heart Association wrote in a statement . Specifically, the research shows that "people are four times more likely to have a heart attack and five times more likely to have a stroke in the month following a laboratory-confirmed case of the flu."

But how can this link be explained? During a viral infection (for example, the flu), the body responds by triggering inflammation as well as an increased tendency to clot blood—two phenomena that can persist after the initial infection has cleared. Both inflammation and clotting can reduce the heart's ability to function properly, which could explain the increased risk of heart attacks and strokes, explains the American Heart Association. Inflammation is also known to contribute to the formation and rupture of plaques in the arteries, thus causing heart attacks and strokes.

The good news is that it's possible to reduce these risks through vaccination. "Preventive measures against viral infections, including vaccination, can play a significant role in reducing the risk of cardiovascular disease. Prevention is particularly crucial for adults who already have heart disease or risk factors," emphasized Dr. Kosuke Kawai, lead author of the study. This has been proven: a study published in 2022 concluded that people vaccinated against the flu have a 34% lower risk of major cardiovascular events, such as heart attacks or strokes.

Last June, the European Society of Cardiology announced that "all available data indicate that vaccination must become a fundamental pillar of prevention strategies, alongside other already established measures" such as reducing blood pressure and cholesterol. One more reason to get vaccinated against the flu! The vaccination campaign, combined with the Covid-19 campaign, began in mid-October in France. Last year, only half of those over 65 and a quarter of those under 65 at risk were vaccinated against the flu, according to the national health insurance system .