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Clinical Reference Systems: Pediatric Advisor 10.0

Infectious Mononucleosis (for Teenagers)


  • severe sore throat
  • large red tonsils covered with pus
  • swollen lymph nodes in the neck, armpits, and groin
  • fever for 7 to 14 days
  • enlarged spleen (in 50% of teens)
  • blood smear showing many atypical (unusual) lymphocytes
  • positive blood test for mononucleosis.


Mononucleosis (mono) is caused by the Epstein-Barr virus (EBV). This virus is transmitted in infected saliva through coughing, sneezing, and kissing. Although mononucleosis can occur at any age, it occurs more often in 15- to 25-year- olds, possibly because of more intimate contacts with others. Contrary to popular belief, mono is not very contagious. Even people in the same household rarely come down with it.


Most teens have only mild symptoms for a week. Even those with severe symptoms usually feel completely well in 2 to 4 weeks.

Complications are rare and require hospitalization when they occur. The most common complication is dehydration from not drinking enough fluids. Breathing may be obstructed by enlarged tonsils, adenoids, and other lymph tissue in the back of the throat. On rare occasions, the enlarged spleen will rupture if the abdomen is hit or strained. Because over 90% of people with mononucleosis will develop a severe rash if they take ampicillin or amoxicillin, these medications should be avoided in this condition.


The symptoms of chronic fatigue syndrome are fatigue, tiredness, weakness, recurrent pains, and the need for more sleep. The symptoms are present for at least 6 months.

There is no good scientific evidence to support mononucleosis as the cause of chronic fatigue syndrome. In general mononucleosis neither lingers nor gets worse. All symptoms are gone within 4 weeks after they first appear. In fact, recent evidence points to a retrovirus as the cause of chronic fatigue syndrome.

Lab tests of the saliva of people who have chronic fatigue syndrome have found the Epstein-Barr virus in the saliva. Tests of their blood have detected antibodies to this virus. These lab results have caused some confusion about the cause of chronic fatigue syndrome. However, 10% to 20% of healthy adults who had mono in the past have the Epstein-Barr virus in their saliva because the virus periodically reappears without any symptoms. Also, the number of mononucleosis antibodies in the blood increases when a person gets new infections by other viruses. Neither the presence of EBV in saliva nor mononucleosis antibodies in the blood means that a person has mononucleosis again.


  1. Fever and pain medicines

    No specific medicine will cure mononucleosis. However, symptoms can usually be helped with medicines. The pain of swollen lymph nodes and fever over 102 degrees F (39 degrees C) can usually be relieved by appropriate doses of acetaminophen or ibuprofen.

  2. Sore throat treatment

    Sipping warm chicken broth can be helpful. Sucking on hard candies can also relieve symptoms (butterscotch seems to be a soothing flavor). Because swollen tonsils can make some foods hard to swallow, eat soft foods as long as necessary. To prevent dehydration, be sure that you drink enough fluids. Milk shakes and cold drinks are especially good. Avoid citrus fruits. Take a daily multiple vitamin pill until the appetite returns to normal. Again, acetaminophen or ibuprofen can be very helpful.

  3. Activity

    You don't need to stay in bed. Bed rest will not shorten the course of the illness or reduce symptoms. You can decide how much rest you need. Slow down some until you no longer have a fever.

  4. Precautions for an enlarged spleen

    Your spleen may be enlarged while you have mononucleosis. A blow to the abdomen could rupture the enlarged spleen and cause bleeding. This is a surgical emergency. Therefore, all teens with mononucleosis should avoid contact sports for at least 4 weeks. Athletes especially must restrict their activity until the spleen returns to normal size (as determined by a physical exam).

    Constipation and heavy lifting should also be avoided because of the sudden pressures they can put on the spleen.

    Your physician will check you weekly until your spleen returns to a normal size.

  5. Contagiousness

    Infectious mononucleosis is most contagious while you have a fever. After the fever is gone, the virus is still carried in the saliva for up to 6 months, but in small amounts. Overall, mononucleosis is only slightly contagious from contacts. Boyfriends, girlfriends, roommates, and relatives rarely get it. The person with mononucleosis does not need to be isolated. However, use separate drinking glasses and utensils and avoid kissing until the fever has been gone for several days.

    The incubation period for mononucleosis is 4 to 10 weeks after contact with an infected person. This means that if a person does become infected with the virus, the symptoms will not appear until 4 to 10 weeks after the contact.


  • Breathing becomes difficult or noisy.
  • Abdominal pain occurs (especially high on your left side).
  • You start feeling very sick.


  • You can't drink enough fluids.
  • Signs of dehydration occur.
  • Sinus or ear pain occurs.
  • You aren't back to school by 2 weeks.
  • Any symptoms remain after 4 weeks.
  • You have other questions or concerns.

Written by B.D. Schmitt, M.D., author of "Your Child's Health," Bantam Books.
Copyright 1999 Clinical Reference Systems