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March 17, 2015

Infectious Mononucleosis

JAMA. 2015;313(11):1180. doi:10.1001/jama.2015.159

Infectious mononucleosis, also known as “mono,” is an illness that usually affects adolescents and young adults.

Cause of Infectious Mononucleosis

Infectious mononucleosis (“mono”) is caused by an Epstein-Barr virus (EBV) infection. Epstein-Barr virus is a member of the herpesvirus family and is one of the most common viruses that infects humans. Most Americans have had an EBV infection by age 40 years.

Epstein-Barr virus is spread through bodily fluids. It is most commonly transmitted through saliva, which is why mono is sometimes called “the kissing disease.” You can also become infected with EBV by sharing a drinking glass, utensils, or a straw with a person who is infected. The virus can also be transmitted through mucus, blood, semen, or vaginal secretions.


For some people, especially young children, an EBV infection does not cause any symptoms. Others may develop a brief illness that is milder than mono. For those who develop mono, symptoms appear 4 to 6 weeks after the time of infection.

The symptoms of mono are common to many infections. You might think you have a cold, the flu, or strep throat. Fatigue is often more severe with mono than with other viral or bacterial illnesses. Some other viral illnesses, such as cytomegalovirus and acute human immunodeficiency virus (HIV), can cause symptoms that are very similar to those of mono.

Common symptoms of mono include

  • Fatigue

  • Fever

  • Sore throat

  • Swollen lymph nodes, especially in the neck

  • Body aches

  • Loss of appetite

Rash is another common symptom. You are more likely to develop a rash if you take ampicillin or amoxicillin (medications used to treat certain bacterial infections).

Most symptoms go away in 2 to 4 weeks, but you might continue to feel tired for several weeks or even months.

Diagnosis and Treatment

A doctor may suspect mono based on symptoms. A blood test can confirm the diagnosis.

There are no medications to treat the infection itself. Antibiotics do not help because antibiotics do not work against viruses, including EBV. You can treat the symptoms of mono, however. Over-the-counter medications such as acetaminophen and ibuprofen can decrease pain and fever. Throat lozenges and gargling with warm salt water may help a sore throat. Resting and drinking plenty of fluids are important.

What Else Do You Need to Know?

A person can spread the EBV virus to other people before having any symptoms of mono and for months after symptoms go away.

Death due to mono is very rare. If you are diagnosed as having mono, you should not play contact sports or do very strenuous activity, such as weight lifting, for at least 4 weeks because your spleen may be enlarged and could rupture. If you develop sudden, severe abdominal pain or difficulty breathing, call 911 or go to an emergency room.

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Article Information

Sources: Centers for Disease Control and Prevention, American Academy of Pediatrics, National Library of Medicine

Topic: Infectious Diseases