Mononucleosis is not a sleep disorder per se, but because it is so common and the fatigue can be so debilitating, it is worth a closer look. It is sometimes called the "kissing disease" and is characterized by fever, infection of the tonsils or throat, and the swelling of lymph nodes. It is caused by the Epstein-Barr virus (EBV), which is quite common, eventually infecting 90 to 95 percent of all adults. This virus is spread by personal contact. Mono can also be caused by cytomegalovirus (CMV).
As part of this illness, people often experience fatigue that may be persistent and severe. In a study of 150 patients, fatigue resolved slowly and was still present in 13 percent of people at six months. It appears to be more common and severe in women compared to men, especially among college students.
In very severe cases, mononucleosis may result in other neurologic symptoms. These can include meningitis and encephalitis, which are infections of the brain or the tissues surrounding the brain and spinal cord called the meninges. This might cause confusion, headache, and drowsiness or coma.
In general, the symptoms of fatigue will gradually resolve over a period of weeks to months. If fatigue persists beyond six months, the condition called chronic fatigue syndrome may be entertained, as EBV has been considered as a possible cause of this disorder.
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Macsween, KF et al. "Infectious mononucleosis in university students in the United Kingdom: evaluation of the clinical features and consequences of the disease." Clin Infect Dis. 2010;50(5):699-706.
Rea, TD et al. "Prospective study of the natural history of infectious mononucleosis caused by Epstein-Barr virus." J Am Board Fam Pract. 2001;14(4):234-42.
Schellinger, PD et al. "Epstein-Barr virus meningoencephalitis with a lymphoma-like response in an immunocompetent host." Ann Neurol. 1999;45(5):659-62.