Multiple sclerosis (MS) is an unpredictable, often disabling disease of the central nervous system that disrupts the flow of information within the brain, and between the brain and body. In multiple sclerosis, damage to the myelin in the central nervous system (CNS) — and to the nerve fibers themselves — interferes with the transmission of nerve signals between the brain and spinal cord and other parts of the body. MS is thought to affect more than 2.3 million people worldwide. While the disease is not contagious or directly inherited, epidemiologists — scientists who study patterns of disease — have identified factors in the distribution of MS around the world that may eventually help determine what causes the disease. These factors include gender, genetics, age, geography and ethnic background. (National Multiple Sclerosis Society, 2017)