Description: Viruses that linger in the body long after the symptoms of an infection have subsided have been linked to a number of different diseases and conditions. It's well known, for example, that the Epstein-Barr virus (EBV) causes infectious mononucleosis, a disease that is often acquired during adolescence. But few people realize that this common virus has also been linked to some cancers and, recently, multiple sclerosis (MS).