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Infectious mononucleosis is sometimes called mono or the kissing disease. It is caused most often by the Epstein-Barr virus (EBV), which is in the herpesvirus family of organisms. Most people become infected with EBV at some point in their lives. Like all herpesviruses, EBV stays within the body once a person is infected. Most of the time, the virus is in an inactive (latent) state, but occasionally the virus multiplies and is shed in saliva and other body fluids.

Getting the Facts About Infectious Diseases

Epstein-Barr virus is spread from one person to another in saliva, blood, and other body fluids. Close contact is usually required, such as kissing or sexual contact.

Although the infection can occur at any age, mononucleosis is most common in people between 15 and 30 years of age.

Signs and Symptoms

Many infants and young children infected with EBV have no symptoms or only very mild ones. When there are signs and symptoms of mononucleosis, they usually include the following:

  • Fever
  • Sore throat, including white patches in the back of the throat
  • Swollen lymph glands in the back of the neck, groin, and armpit
  • Fatigue

In addition to these classic symptoms, some children may also have one or more of the following signs and symptoms:

  • Chills
  • Headache
  • Decreased appetite
  • Puffy eyelids
  • Enlargement of the liver and spleen
  • Oversensitivity to light
  • Anemia

Some children with EBV infection develop meningitis, brain inflammation (encephalitis), and a paralyzing disorder called Guillain-Barré syndrome. Occasionally, EBV can cause myocarditis (inflammation of the heart muscle), an abnormal decline in the number of blood platelets (thrombocytopenia), and inflammation of the testes (orchitis).

This virus can cause several types of cancer. In Africa, EBV causes Burkitt lymphoma; in Asia, nasopharyngeal cancer; and in the United States, a type of lymphoma. However, cancer caused by EBV is rare. It is not clear why some people infected with the virus get cancer while the vast majority does not. In patients with organ transplants, EBV can cause a malignant disorder called lymphoproliferative disease.

There is a rare genetic disease, seen mostly in boys, in which the body cannot control the EBV infection. This serious infection may lead to liver failure, decreases in the blood cells, or cancer and is often fatal. The incubation period of infectious mononucleosis ranges from 30 to 50 days.

When to Call Your Pediatrician

Contact your pediatrician if your child has the major symptoms described here, especially a fever, sore throat, fatigue, and enlarged glands.

How Is the Diagnosis Made?

The diagnosis of infectious mononucleosis is usually made through a medical history, physical examination, and blood tests. These tests may include a complete blood count to check for unusual looking white blood cells (atypical lymphocytes). Blood tests can also detect increases in antibodies against EBV.


Much of the treatment for mononucleosis is aimed at making your child more comfortable until the infection goes away on its own. For example

  • Some pediatricians may recommend giving your youngster acetaminophen to reduce the fever and ease pain.
  • Sore throats can be treated by gargling with warm water and salt.
  • Bed rest can be important for a child feeling fatigued.

Because a virus causes mononucleosis, infected children should not be treated with antibacterials.

In a small percentage of EBV-infected children, corticosteroids such as prednisone are given, but only if certain complications are present, such as inflamed tonsils that may block the breathing passages.

Children with infectious mononucleosis should not participate in contact sports until the swelling of their spleens subsides. If the body is hit in the area of an enlarged spleen, the spleen can rupture or tear open, causing internal bleeding that can lead to death. Keep in mind that this is uncommon and that mononucleosis rarely results in death.

What Is the Prognosis?

Most cases of infectious mononucleosis clear up in 1 to 3 weeks (although symptoms, particularly fatigue, can last for several additional weeks in some children). Patients with abnormal immune systems can have a more severe infection that further weakens the immune system, resulting in cancers or death caused by liver failure and bacterial infections.


It is difficult to prevent the spread of this virus because people who have been infected can spread the virus for the rest of their lives. Your youngster should avoid infected saliva by not sharing drinking glasses, water bottles, or eating utensils.

No vaccine is available to protect against infectious mononucleosis.

Prevention Tip

When to share and when not to share? Your child should not share drinking glasses, water bottles, or eating utensils, which can carry infected saliva.

Last Updated
Immunizations & Infectious Diseases: An Informed Parent's Guide (Copyright © 2006 American Academy of Pediatrics)
The information contained on this Web site should not be used as a substitute for the medical care and advice of your pediatrician. There may be variations in treatment that your pediatrician may recommend based on individual facts and circumstances.
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