Multiple sclerosis is a chronic degenerative disease of the central nervous system. Nationwide, there are an estimated 250,000 to 350,000 people with MS. Researchers have long wondered how MS develops and why it targets certain individuals, though they have long suspected that a virus was involved. Alberto Ascherio, associate professor in the Departments of Epidemiology and Nutrition at the Harvard School of Public Health, said, “For decades it has been suspected that multiple sclerosis is caused by some form of infection in genetically susceptible individuals, but the microorganisms that are responsible for it have remained elusive.” However, a discovery by Ascherio and colleagues seems to pinpoint the common Epstein-Barr virus as a possible agent in causing MS. “Our results suggest that Epstein-Barr virus may be the culprit or, at least one of the culprits,” Ascherio said. The study results appeared in the December 26, 2001 issue of the Journal of the American Medical Association.