Infectious mononucleosis is an illness caused by the Epstein-Barr virus. The symptoms of "mono," as the disease is colloquially called, include extreme fatigue, fever, sore throat, enlargement of the lymph nodes in the neck, armpit, and throat, sore muscles, loss of appetite, and an enlarged spleen. More infrequently, an individual will experience nausea, hepatitis, jaundice (which indicates malfunction of the liver), severe headache, chest pain, and difficulty breathing. Children may display only a few or none of these symptoms, while all can be present in adolescents.

The illness can be passed from person to person via the saliva. In adolescents, mononucleosis was once known as "the kissing disease" since kissing is a route of transmission of the Epstein-Barr virus. Given the relative ease of transmissions, epidemic outbreaks of mononucleosis can occur in environments such as schools, hospitals and the workplace.

Infectious mononucleosis is usually self-limiting. Recovery...