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Last Updated: Mar 1, 2019


Usually a viral infection like a cold or the flu is not cause for alarm (though we should always take the flu seriously). But in rare cases, these viruses can cause a potentially dangerous heart condition called myocarditis.

The heart is a muscular organ that pumps blood through a system of vessels to almost every cell in the body. This process, called circulation, supplies the cells with oxygen and carries off waste products. The heart is divided into four hollow chambers that contract to squeeze blood through the vessels.

Myocarditis is the inflammation (swelling) of the middle layer of the heart’s muscular wall, also known as the myocardium. The condition causes the heart to enlarge and thicken, weakening the chambers inside and reducing the heart’s ability to pump blood.

Mild myocarditis usually isn’t dangerous. However, more serious cases may lead to:

In a few cases, myocarditis can cause permanent damage to the heart, requiring lifelong medical care. In fact, about 45 percent of heart transplants in the United States are performed on people with myocarditis and a related disorder called idiopathic dilated cardiomyopathy.

Fortunately, myocarditis is pretty rare, with only a few thousands cases diagnosed each year in the United States. While exact numbers aren’t clear, it’s believed to occur during 1 to 5 percent of viral infections. Most of these cases are mild, have no heart-related symptoms, and are never diagnosed by a doctor.

Unlike other types of heart disease, myocarditis often strikes younger people with otherwise healthy hearts. Groups at increased risk include children (especially newborns), pregnant women and people with HIV infection.


Myocarditis develops when a pathogen (germ) infects the myocardium. The germ travels to the heart through the blood vessels, enters the myocardium cells and reproduces there. The body then sends special immune cells to fight the disease. Sometimes this immune response is so strong that it damages the heart along with the germ.

Viruses (including some very common ones) are the most common cause of myocarditis:

Less common causes include:


People with mild myocarditis often don’t have any heart-specific symptoms. However, they usually notice signs of an underlying infection, including body aches, joint pain, fever, sore throat, upset stomach, and diarrhea.

Heart-specific symptoms usually appear one to two weeks after the start of the underlying illness. The first is often shortness of breath during physical activity. This typically worsens and may eventually occur at rest or interfere with sleep.

Other common symptoms:

Myocarditis may look slightly different in babies and young children. Common pediatric symptoms include:


Anyone experiencing shortness of breath, chest pain or arrhythmia should seek medical attention. People with very mild symptoms can sometimes wait for a doctor’s appointment, but those with more serious symptoms should go to the nearest emergency department.

Myocarditis is diagnosed based on:


The treatment of myocarditis depends on the underlying cause. Goals of care include:

People with mild myocarditis can often recover at home. Patients with arrhythmia or heart failure may need to stay in the hospital or even intensive care.

Many medications can help to manage myocarditis. In severe cases, they’re often given intravenously.

Severe myocarditis cases might require:

People recovering from myocarditis should rest and avoid exertion while the heart muscle heals. Heart failure patients may also benefit from a low-salt diet and fluid restrictions.


With proper treatment, about two-thirds of people with myocarditis recover completely. The remaining third experience long-term problems with arrhythmia and heart failure that require ongoing medication and management.

About 10 to 15 percent of myocarditis patients later have a recurrence. This can lead to cardiomyopathy, or chronic swelling of the heart. The symptoms and treatment of cardiomyopathy are similar to those of myocarditis.


The best thing you can do to prevent myocarditis is to avoid infections known to cause the condition:


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Tina Shahian, PhD

Tina is a writer for Innerbody Research, where she has written a large body of informative guides about health conditions.


A communication specialist in life science and biotech subjects, Tina’s successful career is rooted in her ability to convey complex scientific topics to diverse audiences. Tina earned her PhD in Biochemistry from the University of California, San Francisco and her BS degree in Cell Biology from U.C. Davis. Tina Shahian’s Linkedin profile.


In her spare time, Tina enjoys drawing science-related cartoons.