Infectious mononucleosis is an acute infection stemming from the Epstein-Barr virus or, more rarely, the cytomegalovirus, both members of the herpes family. It most often affects children, adolescents, and young adults and is particularly common among college students in the early fall and again in the spring. Once the virus enters the body, it multiplies in lymphocytes, a type of white blood cell. The characteristic sore throat, fever and debilitating fatigue usually emerge after an incubation period of about 10 days in children and from 30 to 50 days in adults. Acute symptoms usually disappear after about six to 10 days, although some residual weakness and fatigue may linger for two to three months. Mononucleosis is usually not serious; major complications—which may include infection of the brain or heart or rupture of the spleen—are very rare.

What Causes Mononucleosis (Infectious)?

  • Mononucleosis is frequently transmitted via saliva, hence the nickname “the kissing disease.” It may also be spread via mouth-to-hand-to-mouth contact or by sharing towels, straw or utensils.
  • It’s spread through coughing and sneezing or any contact with someone who has been infected with the virus.
  • The infection may be transmitted during a blood transfusion or transmitted sexually.

Symptoms of Mononucleosis, Infectious

  • Headaches
  • Weakness and fatigue
  • Sore throat and enlarged tonsils
  • Swollen lymph glands in the neck, armpits, and groin
  • Fever and chills (with fluctuating temperatures that peak during the evening at about 101°F to 102°F)
  • Loss of appetite
  • Stiff or sore muscles
  • Temporary jaundice, due to mild, reversible liver damage
  • Enlarged spleen
  • Skin rash
  • Nausea and vomiting
  • Joint pain
  • Fatigue
  • Swollen lymph nodes in the neck and underarms
  • Night sweats
  • Enlarged lymph glands in the groin, armpit and particularly in back of the neck
  • White patches at the back of the throat
  • Hypersensitivity to light
  • Puffy eyelids
  • Anemia

Prevention of Mononucleosis, Infectious

  • Avoid mouth-to-mouth or hand-to-hand contact as well as sharing towels or utensils with persons known to be infected with mononucleosis.

Diagnosis of Mononucleosis, Infectious

  • Diagnosis is suspected in those who exhibit the classic triad of symptoms—sore throat, swollen lymph glands and fever—upon physical examination. An enlarged spleen may also be identified.
  • A high white cell count and the presence of “atypical” lymphocytes in the blood are characteristic findings.
  • A positive heterophile antibody test (a blood test that reveals the presence of specific antibodies against the virus) confirms the diagnosis.
  • Liver function tests may be done.

How to Treat Mononucleosis, Infectious

  • There is no specific treatment for infectious mononucleosis; however, the vast majority of people recover on their own within four to six weeks. Bed rest is essential when symptoms are most acute. A normal schedule of activity can be gradually resumed as symptoms subside.
  • Take over-the-counter analgesics to reduce fever and to relieve headaches, body aches, and sore throat. (Children should be given acetaminophen instead of aspirin.)
  • Drink water and fruit juice to help relieve fever and prevent dehydration.
  • Gargle with one-half teaspoon of salt in a glass of warm water several times a day to relieve sore throat.
  • In rare cases corticosteroids may be prescribed to reduce tonsil inflammation, should it become severe enough to obstruct breathing.
  • Approximately 20 percent of those with infectious mononucleosis will also be simultaneously infected with strep throat, which requires antibiotic therapy for at least 10 days.
  • In rare cases mononucleosis causes a rupture of the spleen, requiring immediate emergency surgery.

When to Call a Doctor

  • If you experience any of the symptoms of infectious mononucleosis, call a doctor.
  • EMERGENCY If you have been diagnosed with infectious mononucleosis and you feel sudden sharp pains in the upper left side of your abdomen, get professional medical care immediately. This may be an indication of a ruptured spleen.


Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference

Simeon Margolis, M.D., Ph.D., Medical Editor

Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50

Updated by Remedy Health Media

Publication Review By: the Editorial Staff at

Published: 25 Aug 2011

Last Modified: 28 Jan 2015