The worldwide prevalence of MS is the absolute lowest around the equator and prevalence increases the further away from the equator you get. Canada, for instance, has a very high prevalence.
MS usually develops in people between 20-40 years of age, but it can occur at all ages. The cause of MS has still not been found and it is also unknown why it develops in women three times more often than in men.
MS in the US
Because the Center for Disease Control and Prevention (CDC) does not require U.S. physicians to report new cases, and because symptoms can be completely invisible, the prevalence of MS in the U.S. can only be estimated. It is believed that there are currently about 250,000 to 350,000 people in the United States who have been diagnosed with multiple sclerosis. This estimate suggests that approximately 200 new cases are diagnosed each week. The number of people who have it compared to the general population is nearly 90 cases per100,000 people. There are about 200 new cases that are diagnosed every week in the country.
It is estimated that there are between 110 to 140 cases of MS per 100,000 people in the Northern States. MS rates in the northern part of the country are twice as high as in the southern parts of the United States.