Thirteen percent of the confirmed measles cases in the U.S. this year have resulted in hospitalization, according to the CDC, including 21% of cases in children five or younger. Three people are confirmed to have died. At the same time, experts stress that this issue goes beyond measles.

The number of reported measles cases in the United States has hit 1,288 in the first six months of this year, the most since the disease was declared eliminated in 2000.

Measles cases in the United States have reached their highest number in more than 30 years, according to new federal data published Wednesday.