An acute viral infection in which the patient develops a sore throat, swollen lymph glands and fever. Also known as glandular fever, infectious mononucleosis is caused by members of the herpes group of viruses – the EPSTEIN BARR VIRUS and CYTOMEGALOVIRUS (CMV). The blood contains many atypical lymphocytes (see LYMPHOCYTE) and the diagnosis is confirmed with the heterophil antibodies test. Patients normally recover within six weeks without treatment, but they may feel tired and depressed for several months afterwards. Some cases of MYALGIC ENCEPHALOMYELITIS (ME) and other chronic fatigue syndromes occur after infection with this virus and, in the long-term, there may be an association with certain types of LYMPHOMA.