Causes of Myocarditis

Causes of Myocarditis

As a rare disease, information about myocarditis has often been scarce – even among healthcare professionals. The Myocarditis Foundation is committed to providing the facts about this condition, which affects millions of people in the United States each year, to keep patients, loved ones, and physicians informed. Here, Dr. Bettina Heidecker offers answers to frequently asked questions about the causes of myocarditis to help clarify how this serious disease occurs.

Dr. Bettina Heidecker

What are the most common causes of myocarditis?

Viral infections are the leading cause of myocarditis. However, a wide range of infections, diseases, and substances may cause this condition, including:

  • Bacteria
  • Fungi
  • Medications
  • Toxins
  • Ticks, spiders, and other biting/stinging insects

Autoimmune conditions, such as lupus, rheumatoid arthritis, and other disorders, have also been proven as a cause of myocarditis.  In rare cases, these may lead to giant cell myocarditis.

How do we know viruses are a leading cause of myocarditis?

The classic presentation of myocarditis is chest pain occurring 1-2 weeks after a viral infection of the upper respiratory or gastrointestinal tract.  During the 1950s and 1960s, researchers conducted experimental and epidemiological studies that examined antibodies in the hearts of patients with myocarditis. These studies revealed enteroviruses, such as Coxsackie virus, in many. Also, myocarditis may be triggered by a viral infection. However, by the time of symptom onset, the virus may have been already eliminated from the blood stream, while the inflammation may be ongoing as shown in a recent study “Virome Sequencing in Patients With Myocarditis”.  In those cases, no traces of the virus can be detected in the peripheral blood.

Which viruses cause myocarditis?

The known viral causes of myocarditis include:

Parvovirus B19

Parvovirus B19 spreads via respiratory droplets that are expelled when infected people cough, sneeze, or speak. Approximately half the population carries its antibodies. It is the cause of fifth disease, sometimes called slapped cheek syndrome for the red facial rash caused in children ages six to 10. Teens and adults typically experience rashes elsewhere, especially the hands and feet. Symptoms of infection usually occur within a week of exposure and last for approximately one week. Parvovirus B19 has also been associated with:

  • Severe birth defects
  • Miscarriage
  • Infection in patients with acquired immunodeficiency syndrome (AIDS), arthritis, and aplastic anemia (lack of red blood cell production)

At this time, there is no vaccination against parvovirus B19.

Human Herpes Virus 6

This virus is transmitted via saliva and often presents with a rash and fever. It is so common that most infants are exposed by 13 months of age, although infection may occur during the first weeks of life. Approximately 20% of infant emergency department visits are linked to fevers caused by human herpes virus 6. Conditions associated with this virus include:

  • Sixth disease (roseola infantum)
  • Hepatitis
  • Encephalitis
  • Multiple sclerosis
  • Chronic fatigue syndrome
  • Fibromyalgia
  • And more…

Once contracted, the virus remains in the salivary glands and bone marrow for life.


These viruses include Coxsackie A virus, or hand, foot, and mouth disease, and Coxsackie B virus, which typically presents as a mild rash, nasal and throat infections, and symptoms commonly associated with colds. It has been known to cause not just myocarditis but also:

  • Pericarditis, or the inflammation of the membrane that surrounds the heart
  • Meningitis, or inflammation of the spinal cord’s outer membranes
  • Pancreatitis, or inflammation of the pancreas

What bacteria can cause myocarditis?

Myocarditis is associated with two types of bacteria that are extremely common and usually harmless unless complications occur. These include:

Corynebacterium diphtheriae

This is the cause of diphtheria. This bacterium most often occurs in school-age children, older adults, and individuals with compromised immune systems. It causes diphtheria, a contagious infection that results in the death of cells inside the throat and tonsils and the formation of pseudomembranes in the back of the throat. This condition can be reliably prevented via immunization.

Staphylococcus aureus

This bacterium usually occurs as part of overwhelming bacterial growth in the blood, a condition called sepsis. Myocarditis was once a very common complication of sepsis, although today, antibiotics help prevent it in many cases.

Which parasites cause myocarditis?

Parasites commonly travel from animal hosts to humans when ticks and insects feed on both. These parasites often cause Lyme disease and most often occur in areas with the greatest incidences of this disease, including the upper Mid-West, Northeast, South, and Western U.S. Myocarditis-causing parasites include:

Borrelia burgdorferi

Once inside the human bloodstream, B. burgdorferi grows and often causes a rash and a host of non-specific symptoms, including fatigue, fever, headache, and muscle and joint aches. While antibiotics can eliminate the parasite, it is often overlooked because the symptoms align with those of the common cold or flu. Without treatment, the bacteria may cause myocarditis and:

  • Facial palsy (drooping)
  • Meningitis (brain infection/inflammation)
  • Joint pain
  • Heart palpitations


This bacteria lives within the monocytes, a special type of white blood cell, and is found in white-tailed deer and mice. Symptoms include rapid-onset high fevers, fatigue, muscle aches, and headache within a week of a tick bite and often resolve without intervention. In more serious cases patients experience myocarditis and/or:

  • Low white blood cell and platelet counts
  • Anemia
  • Loss of liver function
  • Kidney failure

Ehrlichiosis is usually diagnosed via blood work that tests the white blood cells and a clinical history that reviews past tick bites, fever, and other symptoms.


The cause of babesiosis, Babesia is a protozoan that infects the red blood cells. Approximately 25% of adults and 50% of children diagnosed with babesiosis will have no symptoms, while others are at risk for myocarditis and:

  • Anemia
  • Shortness of breath
  • Jaundice
  • Irregular fevers
  • Chills
  • Headaches
  • Lethargy
  • Pain
  • Flu-like symptoms and a sense of disease

Babesiosis may be eliminated via antibiotics in most cases, although more severe cases will require blood transfusions/exchanges.

Trypanosoma Cruzi

This small parasite also infects the red blood cells and causes Chagas disease. Infection occurs when kissing bugs or triatomine bugs feed on wild or domestic animals and later feed on humans, usually in their sleep. Once inside the body, the parasite travels inside red blood cells, replicates, and then causes the cells to burst. Chagas disease most often presents with localized swelling at the site of infection and is frequently undiagnosed. When undetected for decades, it may cause organ failure, as well as myocarditis.

Acute cases can be treated with anti-parasitic drugs, although no treatment exists for chronic conditions. This disease is most common in South America and rarely occurs in the U.S.

What non-infectious factors cause myocarditis?

In some cases, the drugs prescribed to protect our health can also cause myocarditis. These include anti-cancer drugs, antibiotics, and anti-seizure medications.

Exposure to a variety of toxins can also result in myocarditis. These include:

How do physicians diagnose the infectious diseases associated with myocarditis?

The diagnosis of a myocarditis-causing infection varies with the cause. Physicians may rely on:

  • Blood smears
  • Molecular tests
  • Serology, or identifying antibodies produced in response to infection
  • Reports of mild symptoms often associated with Borrelia burgdorferi, Ehrlichia, Babesia, and more
  • Reports of tick bites or exposure to kissing bugs
  • A combination of symptoms in areas where tick- and insect-borne diseases are common

Unfortunately, these infections are often underdiagnosed in regions of the U.S. where tick- and insect-borne infections are less common often mistaken for the cold or flu. Additionally, the high number of infected individuals with no symptoms also contributes to underdiagnosis.

Does infection or exposure to these toxins always cause myocarditis?

No. Most individuals, who are infected with the viruses, bacteria, and parasites noted above, who have severe allergic reactions or who are exposed to these toxins and will never develop myocarditis.

At the same time, it’s important to keep in mind that too few studies have been conducted on the connections between infection, toxins, allergic reactions, and other factors that may cause or contribute to myocarditis. The Myocarditis Foundation seeks to support researchers and physicians engaged in this work to provide greater insight.

Learn More about Myocarditis

If you’ve been diagnosed with myocarditis or have been exposed to one of the causes above, rest assured that physicians are learning more about this condition every day. At the Myocarditis Foundation, we’re committed to offering the support patients and their loved ones need to live with this disease and work toward a brighter future and a cure. Make a donation today to support our mission or contact us for more information.

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