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.

Confirmed measles cases in Texas have reached at least 90, making this the worst measles outbreak in 30 years. Experts warn the number of Texas cases is likely much higher.

The measles outbreak that began in West Texas has now grown to well over 100 cases, with confirmed cases across Texas and New Mexico and possible exposures as far away as San Antonio and San Marcos. From the ongoing outbreak,