It's difficult to avoid the Epstein-Barr virus (EBV). It infects children, adolescents and adults -- 95 percent of American adults between the ages of 35 and 40 have been infected sometime during their lives, so chances are good you and the virus are acquainted [sources: National Center for Infectious Diseases, Andersson]. Once you're infected with EBV, it's with you for life.
EBV is part of the herpes virus family (HHV-4), a family whose members include chickenpox, shingles, and oral and genital herpes, among others. In some people, the virus causes infectious mononucleosis (mono), with fever, fatigue, sore throat and swollen lymph glands as its primary symptoms. Those symptoms last about one to two months, although you may be infected and never have any symptoms.
EBV wasn't always known to cause mono (and, rarely, also Burkitt's lymphoma and some nose and throat cancers). Mono was first described in the Bulletin of the Johns Hopkins Hospital in 1920 (although the illness was recognized earlier than that), but it wasn't until 1964 when mono was linked to HHV-4 by two scientists, Michael Anthony Epstein and Yvonne Barr, and the virus got its name.