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.

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.

LUBBOCK, Texas — A child who was not vaccinated has died from measles in West Texas, the first death in an outbreak that began late last month and the first from measles in the U.S. since 2015.