Myocaditis can be caused by

In the United States, viral infections are the most common cause of myocarditis, with coxsackieviruses A and B and other enteroviruses accounting for a majority of the cases. Cytomegalovirus (CMV), human immunodeficiency virus (HIV), influenza virus, and others are less common pathogens. Toxoplasma gondii (household cats are the most common vector) also can cause myocarditis, paicularly in immunocompromised persons. Trichinosis is the most common helminthic disease with associated cardiac involvement. (Robbins Basic Pathology,9th edition,pg no.401,402)