A total of 839 cases were reported as of last week. That's the most since 1994, when 963 were reported for the entire year.
The Centers for Disease Control and Prevention released the latest numbers Monday.
In all, 23 states have reported cases this year. The vast majority of illnesses have been in New York — most of them among unvaccinated people in Orthodox Jewish communities.
That pattern continued last week, with most of the 75 new cases coming from New York.
Measles was once common in the U.S. but gradually became rare after vaccination campaigns that started in the 1960s.