what groups of people are affected by autism?

All ages, all races, males 4 times more likely than females. If someone develops symptoms of autism above age 3 to 5 (depending upon the diagnoser), than they don't call it autism, they call it some other name, meaning the same thing as autism. Which is a name for a group of symptoms that there is no agreement on cause and no known agreement on successful treatments.

It occurs about in about 5:10,000 children under age 15 years and is 4 more times more common in males then in females.

males more then female, from children all the way up in age.