Every year, unvaccinated travelers (Americans or foreign visitors) get measles while they are in other countries and bring measles into the United States. They can spread measles to other people who are not protected against measles, which sometimes leads to outbreaks. This can occur in communities with unvaccinated people.
Most people in the United States are protected against measles through vaccination. Measles cases in the U.S. are uncommon compared to the number of cases before a vaccine was available. Since 2000, when public health officials declared measles eliminated from the U.S., the annual number of people reported having measles ranged from a low of 37 people in 2004 to a high of 667 people in 2014.