Medical Conditions

Infectious Mononucleosis

by Hal B. Jenson, M.D.
Chief, Pediatric Infectious Diseases
University of Texas Health Science Center
San Antonio, TX
by Charles T. Leach, M.D.
Associate Professor of Pediatrics
University of Texas Health Science Center
San Antonio, TX

What is infectious mononucleosis?

Infectious mononucleosis, also known as "kissing disease," mononucleosis, or, sometimes, just "mono," is an illness characterized by many complaints, but primarily by fever, fatigue, tiredness, enlarged lymph nodes ("lymphadenopathy"), and a sore throat. This disease was originally described in the late nineteenth century as "glandular fever," and it is still known by that name in Europe.


What causes infectious mononucleosis?

The Epstein-Barr Virus (EBV), a DNA virus that is a member of the herpesvirus family of viruses, causes approximately 90% of cases of infectious mononucleosis. Approximately 10% of cases of infectious mononucleosis-like illnesses are caused by primary infection with cytomegalovirus, Toxoplasma gondii, Human Immunodeficiency Virus (HIV), adenovirus, viral hepatitis, and rubella virus.


Who gets infectious mononucleosis?

EBV is found throughout the world and infects more than 98% of the world's population. In underdeveloped and developing countries, and in socio-economically disadvantaged populations of the United States, up to 100% of children are infected with EBV by 2 to 4 years of age. In more affluent populations in the United States, initial EBV infection also occurs more often in young children, but approximately 50% of infection occurs during adolescence and young adulthood. Because initial EBV infection in young children tends to be without any symptoms, most cases of what is diagnosed as infectious mononucleosis occurs in adolescence and young adulthood, even though EBV infection is more common in young children.


How does EBV cause disease?

EBV and the other causes of infectious mononucleosis are transmitted from person-to-person by direct contact or by contaminated secretions of the nose and the mouth. EBV then causes infection in the throat that results in the symptoms of a sore throat and swollen lymph nodes in the neck. The virus then spreads to the white blood cells in the blood stream and causes enlarged lymph nodes in other places throughout the body. The virus, like all other herpesviruses, establishes lifelong infection in the affected person. However, this lifelong infection generally does not cause any symptoms.


What are the common findings?

six weeks. Initial infection in young children is often without any symptoms, or with only mild symptoms. Primary infection in approximately 50% of adolescents and adults appears as fever, fatigue and tiredness, swollen lymph nodes, a sore throat, and, sometimes, an enlarged spleen and liver. Symptoms typically develop over several days and persist for a variable period of days, with gradual spontaneous resolution. The total duration of the disease usually is two to three weeks without complications.


How is infectious mononucleosis diagnosed?

Initially, infectious mononucleosis can be diagnosed in an adolescent or adult on the basis of the typical symptoms-fever, fatigue and malaise, swollen lymph nodes, and a sore throat. The complete blood count may show an uncommon type of white blood cells ("atypical lymphocytes"), which can suggest infectious mononucleosis. The diagnosis is confirmed by checking for antibodies to the virus. If one of the many other causes of infectious mononucleosis is considered, specific blood tests for those causes are available.


How is infectious mononucleosis treated?

There is no specific treatment for infectious mononucleosis. Antibiotics usually are not helpful because the primary cause, EBV, is a virus. Viruses cannot be treated with antibiotics. Antiviral therapy with acyclovir has been shown to decrease viral growth and shedding of EBV from the mouth, but this treatment does not affect the severity of symptoms, the duration of the clinical course, or the eventual outcome.

Infectious mononucleosis is treated primarily with rest and symptomatic therapy. Fever should be treated with acetaminophen or ibuprofen. Because the spleen may be enlarged and may easily rupture, it is advisable to refrain from participation in any contact sports and strenuous physical activities for the first two to three weeks of illness, or, if an enlarged spleen is present, until it has resolved.

Some patients with infectious mononucleosis have such greatly enlarged tonsils that they have difficulty breathing or swallowing. For these patients, steroids have been shown to have a dramatic effect in shrinking enlarged tonsils within 12 to 24 hours. However, most persons with infectious mononucleosis do not require steroids.


What are the complications?

The great majority of patients with infectious mononucleosis recover uneventfully without complications. Some chronic conditions have been suggested to be associated with infectious mononucleosis, but this has not been proved. At present, there is no evidence to support the association of EBV infection with chronic fatigue syndrome or chronic immune dysfunction.

EBV is a virus that has been associated with several human cancers, including nasopharyngeal carcinoma, Burkitt lymphoma, Hodgkin disease, and lymphomas and smooth muscle tumors ("leiomyosarcomas") in individuals with decreased ability to ward off other infections.


How can infectious mononucleosis be prevented?

There is no vaccine for EBV or the other causes of infectious mononucleosis. There is very little information on how to prevent it. Outbreaks are uncommon. Minimizing exposure to the oral secretions of infected persons can prevent the spread of infectious mononucleosis. Most healthy adults excrete EBV from the mouth periodically throughout their lives, with approximately 20% of the healthy adult population excreting EBV at any given time.


What research is being done?

There is much research into the molecular events that are important in the control of EBV after the initial infection resolves. There is interest in developing a vaccine because almost everybody is infected with EBV in childhood and because of the association of EBV with several types of cancer.


About the Authors

Hal Jenson, M.D.





Charles T. Leach, M.D.




Copyright 2012 Hal B. Jenson, M.D., All Rights Reserved