Infectious mononucleosis -- known popularly as "mono" or "the kissing disease" -- has been recognized for more than a century. An estimated 90 percent of mononucleosis cases are caused by the Epstein-Barr virus (EBV), a member of the herpes virus group. Most of the remaining cases are caused by certain other herpes viruses, particularly cytomegalo virus. This fact sheet focuses on mononucleosis caused by EBV. EBV is a common virus that scientists estimate has infected over 90 …showed first 75 words of 1909 total…

…showed last 75 words of 1909 total…of the body to this increase in B cells is a corresponding increase in T lymphocytes, another component of the immune system, which change in appearance to become atypical cells. Some of these T cells apparently limit the spread of the virus from cell to cell; others suppress the production of the B cells. This suppression is what seems to eliminate the infection. Normally, the T cell response subsides as the patient recovers from mononucleosis.