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Mononucleosis (MON-oh-new-klee-OH-siss) is an illness caused by the Epstein-Barr virus (EBV).

“Mono,” as it is sometimes called, is contagious (“catching”). It can be passed from person to person through the saliva. Young children can catch mono by coming in contact with the saliva of infected playmates or family members. Adolescents can spread EBV through kissing, which is why some people call it “the kissing disease.”

Signs and Symptoms

Common symptoms of mono include:

enlarged spleen and lymph nodes

  • Extreme tiredness
  • Fever
  • Sore throat
  • Enlarged lymph nodes (neck, armpits, throat) (Picture 1)
  • Sore muscles
  • Enlarged spleen (an organ that filters the blood and produces antibodies)

Less common symptoms include nausea, severe headache, stiffness, chest pain and trouble breathing. A child who has been treated recently with ampicillin or amoxicillin may have a pink rash all over the body.

Teens may feel very weak and have a poor appetite. They may be so tired and weak that they will stay in bed for more than a week. These signs are more common in teens than in younger children. Younger children may have few of these symptoms. Instead they may just have a slight fever, tiredness and poor appetite.


Epstein-Barr virus is usually diagnosed with blood tests. Blood tests can show antibodies against the EBV virus. If a person has this virus, the tests will also show an increase in the number of white blood cells. There will also be an increase in the number of white blood cells that fight viral infections (lymphocytes – LIMF-oh-sites).


Children and teens usually have the virus for 1 to 2 weeks before they have symptoms. Once symptoms appear, mono usually goes away on its own in a few weeks.

  • The best treatment is plenty of rest and drinking lots of liquids.proper medication that is not Aspirin
  • You may give acetaminophen (such as Tylenol®) or ibuprofen (such as Motrin®) for muscle aches and fever. Do not give aspirin (Picture 2). Giving aspirin can lead to Reye syndrome, a very serious illness.
  • If tonsils or lymph nodes in the neck are very enlarged and cause trouble breathing, the doctor may prescribe a steroid medicine. Because mono is caused by a virus, antibiotics (such as penicillin) will not help unless the child has another infection caused by bacteria.
  • People who have mono should not take part in contact sports or vigorous exercise until the doctor says it is okay. Even playful wrestling at home could harm the enlarged spleen.
  • Avoid rough or active play for one month after recovery.


In rare cases complications of EBV infection can occur. These may include: blood disorders like hemolytic anemia, Bell’s palsy, rupture of the spleen, inflamed heart muscle and nervous system problems, including Guillain-Barré syndrome, a disease that paralyzes the muscles.


There is no vaccine to prevent mono, but people who have had the EBV virus once do not usually get mono again. The best way to prevent mono is to avoid contact (sneezing, coughing and kissing) people who are infected. The virus can stay in the saliva of infected people for several months.

When to Call the Doctor

Call your child’s doctor if any of these things occur:

  • Sudden, sharp pains in the upper left abdomen. Call the doctor right away. This could mean a serious problem with the spleen and should be treated immediately.
  • Any trouble breathing or swallowing.
  • Decreased urine output and dehydration (getting “dried out”).
  • Any other symptoms that get worse or do not go away.

Mononucleosis (Infectious) (PDF)

HH-I-242 11/04 Revised 9/11 Copyright 2004-2011, Nationwide Children’s Hospital