What is already known about this topic?
Measles was eliminated in the United States in 2000.
What is added by this report?
During January 1–April 26, 2019, a total of 704 cases were reported, the highest number of cases reported since 1994. Outbreaks in close-knit communities accounted for 88% of all cases. Of 44 cases directly imported from other countries, 34 were in U.S. residents traveling internationally; most were not vaccinated.
What are the implications for public health practice?
Unvaccinated U.S. residents traveling internationally are at risk for acquiring measles. Close-knit communities with low vaccination rates are at risk for sustained measles outbreaks. High coverage with measles, mumps, rubella (MMR) vaccination is the most effective way to limit transmission and maintain elimination of measles in the United States.