1. An acute infectious disease caused by the Epstein-Barr virus, producing fever, swelling of the lymph nodes, sore throat, and increased lymphocytes in the blood.
2. A specific viral infection with the Epstein-Barr virus in which there is an increase of white blood cells that are mononuclear (with a single nucleus).

"Mono" and "kissing disease" are popular terms for this very common illness caused by the Epstein-Barr virus (EBV); however, by the time most people reach adulthood, an antibody against EBV can be detected in their blood meaning they have been infected with EBV.

The illness is less severe in young children and the infection can be spread by saliva. Symptoms include fever, fatigue, sore throat, and swollen lymph glands.

"Mono" can cause liver inflammation (hepatitis) and spleen enlargement. Vigorous contact sports should be avoided to prevent spleen rupture.

Since mono is caused by a virus and not bacteria, antibiotics are of no benefit; therefore, treatment is directed at relieving the symptoms, which may persist for one to two months.