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.

Measles cases has risen to 124 across several counties in West Texas, and health officials are seeing no clear end in sight to the outbreak. Texas Department of State Health Services confirmed the first death related to the outbreak Wednesday.