Could you please tell me what causes acute myocarditis?

Viral infections: Viral infections like coxsackievirus, parvovirus, and even HIV are believed to be the most common cause of acute myocarditis (inflammation of the heart muscle which results in heart dysfunction). Autoimmune diseases like lupus and rheumatoid arthritis, environmental toxins, drugs like certain antibiotics, alcohol, and cocaine, and radiation are other potential etiologies.

Lots of causes..: But commonly viral ---Coxsackie (A, B), Adenovirus, Influenza (A, B), Herpes simplex, Cytomegalovirus, Varicella-zoster virus, Epstein-Barr virus, Mumps, Rubella, Rubeola, Vaccinia, Rabies, Coronavirus, Hepatitis B, HIV. Other casues include bacteria, parasites, fungi, protozoa, autoimmune, drugs (cardiotoxins), radiation, some systemic disorders (e.g. thyrotoxicosis,s arcoidosis).