At least 124 cases of measles have been identified in Texas since late January, mostly among children and teenagers who are either unvaccinated or whose vaccination status is unknown, officials say.

A child who wasn’t vaccinated died in a measles outbreak in rural West Texas, officials there said Wednesday, the first U.S. death from the highly contagious respiratory disease since 2015.

An unvaccinated child in west Texas died from measles this week, according to a Wednesday news release from the Texas Department of State Health Services. This is the first death from the west Texas measles outbreak that began late last month, and is the first death from measles in the United States since 2015.