infectious mononucleosis is caused by a virus belonging to the herpes virus family, specifically by EBV, the Epstein-Barr virus. It is transmitted from one person to another by direct contact with saliva.
Symptoms include fever, sore and swollen throat, tiredness, malaise, muscle and headache pain, rash and swollen glands in the neck and armpits. The most disabling symptoms such as pain and fever usually disappear in about fifteen days. Only in some cases can it be complicated by anemia, clotting problems, myocarditis or liver problems.