Myocarditis symptoms may not appear immediately; they may develop slowly. Initial symptoms can mimic many illnesses. Generally, symptoms resemble those of illnesses such as the flu and pneumonia. In some individuals, symptoms appear suddenly.

Symptoms of myocarditis (inflammation of the heart muscle) include:

* Chest pain
* Shortness of breath at rest or with exertion
* Swelling in the legs, ankles, and feet
* Rapid or irregular heartbeat
* Unusual fatigue
* Pale skin
* Fever
* Muscle and joint aches
* Loss of appetite
* Nausea
* Unexplained weight loss
* Cough

However, myocarditis symptoms vary from person to person. Symptoms may also differ depending on the severity and duration of the inflammation. A persistent fever, excessive fatigue, and shortness of breath warrant a visit to a doctor.