A Texas measles outbreak has doubled in the last week to 124 cases, state health officials said Tuesday, a day after they warned a person infected with the highly contagious disease had traveled from the outbreak zone.

A child in West Texas has died of measles, state health officials said on Wednesday, the first reported U.S. death from the highly contagious disease in a decade, as a Texas outbreak has grown from a handful of cases to more than 130 across two states.

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