Texas officials on Wednesday announced the first measles death in the state's ongoing outbreak of the highly contagious disease. The death, of a school-age child, is the first measles death in the U.S. since 2015, according to the Centers for Disease Control and Prevention.

An unvaccinated child has died as the Texas measles outbreak reaches 124 cases. Public health officials also warn of potential spread in San Marcos and San Antonio.

The effectiveness of the vaccine, coupled with rising vaccination rates, led to such low rates of measles that it was declared eliminated in the U.S. in 2000. In recent years, though, the virus has made a resurgence, as childhood vaccination rates have dropped nationwide.