Definition of Mononucleosis

Mononucleosis: Infection with the Epstein-Barr virus (EBV, human herpesvirus 4, HHV-4) in which there is an increase of white blood cells that have a single nucleus (monocytes). The infection can be spread by saliva. Its incubation period is four to eight weeks. Symptoms include fever, fatigue, sore throat, and swollen lymph glands. Mononucleosis can cause liver inflammation (hepatitis) and spleen enlargement; vigorous contact sports should be avoided to prevent spleen rupture. It is less severe in young children.

Most people exposed to EBV do not develop mononucleosis: most adults carry an antibody against EBV in their blood, meaning they have been infected with EBV at some time. Treatment includes rest, pain medication, and in some cases anti-viral medication.

Also known as mono, the kissing disease. See also Epstein-Barr virus.