How quickly can myocarditis develop? over days, hours , or weeks?

Myocarditis: Many viruses have been implicated as causes of myocarditis. These most commonly include adenoviruses and enteroviruses such as the coxsackieviruses. Recently, parvovirus B19 has been associated with a significant percentage of patients diagnosed with myocarditis and DCM. Depending on the cause all of your time options are a possibility. Giant Cell myocarditis being one of the most aggressive.