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 tested positive for measles died in West Texas, the state health department said, marking the first death in an outbreak that has sickened nearly 140 people. The Texas Department of State Health Services said a school-age child died after being hospitalized in Lubbock.

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