Infectious mononucleosis or “mono” is caused by Epstein-Barr virus (EBV), a member of the herpes virus family. It’s spread during close physical contact, mostly through transmission of saliva. (That’s pretty close, earning mono its nickname, “kissing disease.”) Ninety percent to 95% of people in the U.S. eventually are infected by EBV, although not all of them develop full-blown mononucleosis.
People can transmit EBV to other people for six months or longer after recovering from mononucleosis. In studies, many people continue to have EBV in their saliva for up to 18 months after symptoms of mono have resolved. That’s why most people who get mononucleosis don’t remember being around (or kissing) someone with mono.
It’s also possible to periodically shed EBV virus in one’s saliva throughout life, without having symptoms. It’s not clear if people commonly transmit the virus during these periods.
Fever, sore throat, fatigue, and swollen tonsils and lymph nodes are the usual symptoms of mono. The worst of the symptoms go away in one to two weeks, but fatigue can last for months.
Vetsika, EK. Expert Reviews in Molecular Medicine, 2004; vol 6(23): pp 1-16.
Fafi-Kremer, S. Journal of Infectious Disease, 2005; vol 191(6): pp 985-989.
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