The Epstein-Barr virus (EBV) may be the leading cause or trigger of multiple sclerosis (MS), a study led by Harvard researchers suggests. MS is a progressive, neurodegenerative disease of the brain and spinal cord that affects 2.8 million people worldwide, nearly 1 million of whom are in the United States. The cause of MS has not been established although many have suspected EBV, a member of the herpesvirus family that can cause infectious mononucleosis, also called “kissing disease.” EBV can also establish a lifelong latent infection in the individual. “The hypothesis that EBV causes MS has been investigated by our group and others for several years, but this is the first study providing compelling evidence of causality,” said Alberto Ascherio, professor of epidemiology and nutrition at Harvard Chan School and the senior author of the study, in a statement. “This is a big step because it suggests that most MS cases could be prevented by stopping EBV …