Mononucleosis (Infectious)

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Infectious mononucleosis (mon oh new klee OH siss), also known as “mono,” is an illness usually caused by the Epstein-Barr virus (EBV). A few cases are caused by a virus called cytomegalovirus (CMV).

The virus easily passes from person to person (contagious) when someone comes in contact with an infected person’s saliva. It can be spread by kissing (this is why some people call it “the kissing disease.”) Children can get mono by sharing things such as cups, straws, toothbrushes or toys that have may have the drool of an infected person on it.

Mono can occur at any age. Most people are infected with the virus at some time in their lives and may not get sick. The virus hides out until the person is run down. This explains why mono is more common in high school and college students. Once a person has had mono, he or she usually does not get it again.

Signs and Symptoms

Children and teens can have the virus for 4 to 7 weeks beforeenlarged spleen and lymph nodes symptoms show up. The most common are:

  • Extreme tiredness
  • Fever
  • Sore throat with or without white patches at the back of the throat
  • Enlarged lymph nodes or swollen glands (neck, armpits, groin) (Picture 1)
  • Sore muscles and stiffness
  • Enlarged liver or spleen (The spleen is an organ that filters the blood and makes antibodies to fight infection.)

Less common symptoms are puffy eyes, nausea, severe headache, sensitivity to light, 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.

Young children typically have milder symptoms, such as a slight fever, tiredness and poor appetite. Teens may have more symptoms and feel so tired and weak that they will stay in bed longer than a week.


The doctor diagnoses mono by health history, physical exam and blood tests. Blood tests show antibodies against the virus. The tests will also show an abnormally high number of white blood cells that fight viral infections.


Because a virus causes mono, antibiotics (such as penicillin) will not help unless the child has another infection caused by bacteria. Mono symptoms usually go away on their own after a few weeks.
The best treatment is getting plenty of rest, drinking lots of liquids and eating healthy.

  • You may give acetaminophen (Tylenol®) or ibuprofen (Motrin®) for sore throat, muscle aches or fever. Do not give aspirin (Picture 2). Giving aspirin can lead to Reye syndrome, a very serious illness.proper medication that is not Aspirin
  • If tonsils or lymph nodes in the neck are very enlarged and cause trouble breathing, the doctor may prescribe a steroid medicine.
  • People who have mono should not do contact sports or vigorous exercise until the doctor says it is okay. Even playful wrestling at home could harm the enlarged spleen.
  • Avoid heavy lifting, rough or active play for one month after recovery.


There is no vaccine to prevent mono. The best way to prevent mono is to stay away from people who are infected. Avoid kissing anyone with mono or sharing drinks, foods or personal items like toothbrushes. Wash hands well and often. Wash dishes and eating tools separately in hot soapy water or in the dishwasher. The virus can stay in the saliva of an infected person for many months, even after he is well.

When to Call the Doctor

Most children who get mono get well without any problems. In rare cases, complications can happen. Call your child’s doctor if any of these things occurs:

  • Sudden, sharp pains in the upper left abdomen (tummy) that last more than 5 minutes. Call 911 or the doctor right away. This could mean a serious problem with the spleen.
  • Any trouble breathing, swallowing or eating
  • Less than usual urine output, along with dehydration (getting “dried out”)
  • Very drowsy, restless or does not respond
  • Any other symptoms that get worse or do not go away

Mononucleosis (Infectious) (PDF)

HH-I-242 11/04 Revised 3/18 Copyright 2004, Nationwide Children’s Hospital