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.

The first person known to have died from measles in the U.S. in a decade was announced by health officials on Wednesday and described as a "school-aged child" who perished in a children's hospital in West Texas,