Infectious mononucleosis is a viral disease that affects certain blood cells. It is caused by the Epstein-Barr virus (EBV), which is a member of the herpesvirus family. Most cases occur sporadically. Outbreaks are rare.
While most people are exposed to the Epstein-Barr virus sometime in their lives, very few go on to develop the symptoms of infectious mononucleosis. In underdeveloped countries, people are exposed in early childhood where they are unlikely to develop noticeable symptoms. In developed countries such as the United States, the age of first exposure may be delayed to older childhood and young adult age when symptoms are more likely to result. For this reason, it is recognized more often in high school and college students.
The virus is spread by person-to-person contact, via saliva (on hands or toys, or by kissing). In rare instances, the virus has been transmitted by blood transfusion.
Symptoms include fever, sore throat, swollen glands and feeling tired. Sometimes, the liver and spleen are affected. Duration is from one to several weeks. The disease is very rarely fatal.
Symptoms appear from four to six weeks after exposure.
The virus is shed in the throat during the illness and for up to a year after infection. After the initial infection, the virus tends to become dormant for a prolonged period and can later reactivate and be shed from the throat again.
No treatment other than rest is needed in the vast majority of cases.
Avoid activities involving the transfer of body fluids (commonly saliva) with someone who is currently or recently infected with the disease. At present, there is no vaccine available to prevent infectious mononucleosis.
Last Reviewed: November 2011