Infectious Mononucleosis known popularly as "mono" is a infectious disease caused by the Epstien-Barr virus in a estimated 90 percent of cases ( EBV ) a member of the herpes family. The remaining cases are caused by a certain herpes virus, or cytomegalovirus. Mononucleosis is taken from the name of the blood's mononuclear cells, white blood cells ( B cells ) increase in the person blood stream when a person has this disease. It is estimated that seventy to eighty percent involve persons between the ages of 15 to 30. This disease is common in both men and women, although it has been documented that this disease affects men slightly more than women. Mononucleosis does not occur during