The first measles death in the growing outbreak in West Texas was a school-aged child. The child was unvaccinated and had been hospitalized in Lubbock, Texas, said Lauren Adams, Lubbock city spokesperson. This is the first US measles death since 2015, when a woman in Washington state died.

A measles outbreak in West Texas has topped 120 cases and resulted in the first U.S. death from the illness in a decade.

Here’s what to know about the outbreak after the first U.S. death since 2015 from the highly contagious—but preventable—respiratory disease.