An unvaccinated child has died from measles in West Texas, officials said, marking the first fatality from the disease in the U.S. since 2015. The Texas Department of State Health Services (DSHS) confirmed the death on Wednesday but did not disclose the patient's age.

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

At least 124 cases have been reported since late January, mostly among children and teenagers who were unvaccinated or whose vaccination status was unknown.