probable link between COVID-19 vaccine and myocarditis cases Myocarditis is an inflammation of the heart muscle (myocardium). Myocarditis can affect heart muscle heart's electrical system, reducing heart’s ability to pump and causing rapid or abnormal heart rhythms (arrhythmias). A viral infection usually causes myocarditis, but it can result from a reaction to a drug or be part of a more general inflammatory condition. Severe myocarditis weakens heart so that the rest of body doesn't get enough blood. Clots can form in heart, leading to a stroke or heart attack. Causes · Viruses . Many viruses are commonly associated with myocarditis, including the viruses that cause the common cold (adenovirus); COVID-19 ; hepatitis B and C; parvovirus, which causes a mild rash, usually in children (fifth disease); and herpes simplex virus. · Bacteria . Numerous bacteria can ca...