Heart attacks may actually be caused by bacterial infections.

A groundbreaking study from Tampere University and the University of Oxford is reshaping our understanding of what causes heart attacks.

Long blamed primarily on cholesterol and lifestyle factors, new research now points to a hidden culprit: bacterial infections.

Scientists discovered that within the fatty plaques of coronary arteries, bacterial biofilms—gel-like communities of bacteria—can lie dormant and undetected for years. These microbial invaders, particularly strains like viridans streptococci commonly found in the mouth, evade immune detection and traditional antibiotics by embedding themselves deep within plaque tissue.

The danger arises when the body is hit with a viral infection, which ramps up immune activity and disturbs the biofilms. That disturbance can reactivate the bacteria, triggering a sudden surge of inflammation. In turn, this can weaken arterial plaques, causing them to rupture and form clots—leading to heart attacks. Researchers were able to map these biofilms in tissue from patients who died from cardiac arrest and found that antibodies could unmask their full structure. This discovery could pave the way for new diagnostics or even vaccines to prevent infection-triggered heart attacks, signaling a major shift in cardiovascular medicine.

Source: Viridans Streptococcal Biofilm Evades Immune Detection and Contributes to Inflammation and Rupture of Atherosclerotic Plaques. Journal of the American Heart Association, 2025.