Health and Me

Rachel V Thomas

Why do heart attacks increase during flu season?

A severe <a href="https://www.healthandme.com/health/influenza">influenza</a> A virus, commonly known as seasonal flu, may not only leave you coughing and feeling feverish, but also silently damage your heart, increasing the risk of heart attacks, according to a study.

A team of researchers from the Icahn School of Medicine at Mount Sinai, New York, US, unraveled that the influenza A virus directly damages the heart by hijacking immune cells. This leads to long-lasting cardiac dysfunction even after the lung infection is cleared.

The study, published in February 2026 in the journal Immunity, focused on an immune cell, known as pro-dendritic cell 3.

The researchers revealed that the pro-dendritic cell 3 acts as the ‘Trojan horse’ of the immune system during flu infection and carries the virus to the heart from the lungs. 

Once in the heart, it produces large amounts of type 1 interferon and triggers the death of cardiomyocytes, impairing cardiac output. 

Importantly, the findings showed that an annual flu vaccine can prevent damage to the heart.

“We have known for years that the frequency of heart attacks increases during flu season, yet outside of clinical intuition, scant evidence exists of the underlying mechanisms of that phenomenon,” said senior author Filip Swirski, Director of the Cardiovascular Research Institute at the Icahn. 

“These findings offer great promise for the development of new therapies, which are desperately needed since there are currently no viable clinical options to prevent cardiac damage,” Swirski added. 

The team studied autopsies of 35 hospitalized patients who died of influenza. Of these, more than 85 percent had at least one significant cardiovascular comorbidity, such as hypertension. A majority of them also had multiple comorbidities, including atherosclerosis and cardiac fibrosis, underscoring cardiovascular disease as a major driver of influenza mortality. 

The study also provided evidence that a cutting-edge modified mRNA treatment that dampens an interferon signaling pathway in the heart can significantly mitigate cardiac damage following viral infection while preserving the protective antiviral response of the immune system. 

“The hopeful news for patients is that by injecting a novel mod-RNA therapeutic that modulates the IFN-1 signaling pathway, we reduced levels of cardiac damage, as evidenced by lower troponin, and improved cardiac function, as measured by higher left ventricular ejection fraction,” explained Jeffrey Downey, a member of Dr. Swirski’s laboratory who served as lead author. 

Global statistics show that influenza A viruses cause an estimated 1 billion infections each year. This ranges from seasonal flu outbreaks locally to pandemics globally. 

While most infections are mild and self-resolving, in some cases, they can become severe or even fatal. When the virus travels to the heart, it triggers the death of cardiomyocytes -- specialized muscle cells that are responsible for the rhythmic contraction and relaxation of the heart.

Health Conditions A-Z

health

Influenza

Heart Attack

Flu (Influenza)

cough

Q Fever

virus

immune cell

lung infection

heart

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A severe influenza A virus, commonly known as seasonal flu, may not only leave you coughing and feeling feverish, but also silently damage your heart, increasing the risk of heart attacks, according to a study. A team of researchers from the Icahn School of Medicine at Mount Sinai, New York, US, unraveled that the influenza A virus directly damages the heart by hijacking immune cells. This leads to long-lasting cardiac dysfunction even after the lung infection is cleared.  The study, published in February 2026 in the journal Immunity, focused on an immune cell, known as pro-dendritic cell 3. The researchers revealed that the pro-dendritic cell 3 acts as the ‘Trojan horse’ of the immune system during flu infection and carries the virus to the heart from the lungs. Once in the heart, it produces large amounts of type 1 interferon and triggers the death of cardiomyocytes, impairing cardiac output. Importantly, the findings showed that an annual flu vaccine can prevent damage to the heart.“We have known for years that the frequency of heart attacks increases during flu season, yet outside of clinical intuition, scant evidence exists of the underlying mechanisms of that phenomenon,” said senior author Filip Swirski, Director of the Cardiovascular Research Institute at the Icahn. “These findings offer great promise for the development of new therapies, which are desperately needed since there are currently no viable clinical options to prevent cardiac damage,” Swirski added. What The Study Found The team studied autopsies of 35 hospitalized patients who died of influenza. Of these, more than 85 percent had at least one significant cardiovascular comorbidity, such as hypertension. A majority of them also had multiple comorbidities, including atherosclerosis and cardiac fibrosis, underscoring cardiovascular disease as a major driver of influenza mortality. The study also provided evidence that a cutting-edge modified mRNA treatment that dampens an interferon signaling pathway in the heart can significantly mitigate cardiac damage following viral infection while preserving the protective antiviral response of the immune system. “The hopeful news for patients is that by injecting a novel mod-RNA therapeutic that modulates the IFN-1 signaling pathway, we reduced levels of cardiac damage, as evidenced by lower troponin, and improved cardiac function, as measured by higher left ventricular ejection fraction,” explained Jeffrey Downey, a member of Dr. Swirski’s laboratory who served as lead author. Influenza A Virus And The HeartGlobal statistics show that influenza A viruses cause an estimated 1 billion infections each year. This ranges from seasonal flu outbreaks locally to pandemics globally. While most infections are mild and self-resolving, in some cases, they can become severe or even fatal. When the virus travels to the heart, it triggers the death of cardiomyocytes -- specialized muscle cells that are responsible for the rhythmic contraction and relaxation of the heart.