The epidemiology of multiple sclerosis: Clues to the etiology of a mysterious disease

The etiology of multiple sclerosis (MS) has not yet been defined. Based on analysis of prevalence, incidence, and migration studies, it is likely that one or more environmental factors, probably infectious in origin, initiates the disease. Canine distemper virus appears to be an attractive candidate in this regard. Because the risk of acquiring MS is greater in multiplex families (particularly in identical twins), certain ethnic and religious groups, and individuals with the human leukocyte antigen DW2, genetic predisposition is an important determinant in disease expression.