While most people know that the flu virus can lead to other health complications, such as pneumonia, bronchitis and bacterial infection of the lungs, recent research reveals that the flu — a common, contagious respiratory illness caused by influenza viruses — can also increase the risk of heart attack and stroke. According to a seven-year case series published in The Journal of Infectious Diseases, adults aged 50 and older who had even a mild case of the flu were shown to have double the risk of suffering a heart attack or ischemic stroke within two weeks after catching the virus. This likelihood quadrupled in adults with preexisting health conditions who dealt with a severe case of the flu, with their risk lasting up to two months post-infection.
Yet this isn’t the first time researchers discovered this link. A 2020 study conducted by the Centers for Disease Control and Prevention (CDC), which involved more than 80,000 adults hospitalized with the flu, reported that 1 in 8 patients (nearly 12%) had an acute cardiac event, such as acute heart failure or acute ischemic heart disease. Also, research published in 2018 in The New England Journal of Medicinefound a significant association between the flu and acute myocardial infarction — otherwise known as a heart attack — where adults were six times more likely to have a heart attack within one week after catching the flu.
What is the connection between the flu and serious cardiac events — and how can adults prevent themselves from becoming a statistic? Three cardiologists explain.
How can the flu cause a heart attack or stroke?
Infections that appear to impact only one part of the body actually tend to affect multiple parts of it, Dr. Gregory Katz,assistant professor in the department of medicine at the Leon H. Charney Division of Cardiologyat NYU Langone Health, tells Yahoo Life.
“The flu can have direct and indirect effects on the heart,” he says. “When it comes to the direct effects, there is a possibility that the flu virus — or really any type of virus — causes inflammation of the heart muscle, which is called myocarditis. It can also cause inflammation around the sac [or lining] of the heart called pericarditis.”
Dr. Majid Basit, a cardiologist with Memorial Hermann in Houston, tells Yahoo Life: “In some cases, the influenza virus can also directly infect the heart cells, leading to weakened heart function and heart failure.”
As for the indirect effects, Katz explains that the immune system works overtime to fight a viral infection, and this response can interfere with the cholesterol buildup in the arteries. Basit agrees and adds that an influenza infection places the body under a tremendous amount of stress. “This stress can lead to a rupture of the cholesterol deposits, leading to a heart attack,” continues Basit. “Additionally, there is an increase in inflammation during an illness, which can make the cholesterol plaques more prone to rupture. A stroke is like a heart attack with plaque rupture, but it occurs in blood vessels supplying the brain.”
Blood pressure levels may also be impacted — another cardiovascular risk factor that can trigger heart attacks and strokes, says Dr. Jim Liu, a cardiologist at The Ohio State University Wexner Medical Center. “In more severe respiratory infections, oxygen levels may become low and blood pressure may become either too high or too low,” he tells Yahoo Life. “And these [fluctuations] can also contribute to increased stress on the heart.”
Both age and health status play vital roles in this connection as well. “People with a weak heart or known heart disease are more prone to a heart attack during an influenza infection,” says Basit. “The elderly are at an even greater risk.”
How can you protect yourself?
The statistics are overwhelming: According to the CDC, there were an estimated 25 million to 46 million cases of the flu between October 2023 and February 2024, while heart disease continues to be the leading cause of death for men and women in most racial and ethnic groups in the U.S. However, the promising news is that preventive measures can be taken to help ward off the flu while also boosting cardiovascular health. For starters, practicing healthy lifestyle behaviors throughout the year can be a highly effective strategy, says Katz.
“In terms of what can you do to protect yourself, the answer is to eat well, exercise regularly, don’t smoke, maintain a healthy weight, reduce stress levels and sleep well,” he recommends. “These strategies are always good advice because as a general rule, healthier people who do get the flu tend to have a milder course of the illness.”
Basit explains that influenza is spread by droplets when people cough or sneeze. “Wearing a mask and making sure to wash your hands frequently — especially after touching common areas, like doorknobs — can also help prevent an influenza infection,” he says.
And lastly, all three cardiologists encourage routine vaccinations. “One of the most important pieces of advice would be to get the annual flu vaccine,” says Liu. “In people with cardiovascular disease or who are at high risk for having cardiovascular disease, the flu vaccine has been shown to help reduce the risk of serious cardiovascular complications from the flu.”
