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 who was not vaccinated has died from measles in West Texas. It's the first death in an outbreak that began late last month and the first from measles in the U.S. since 2015.

According to the society, the last US measles death was in 2015. A measles infection can have particularly devastating complications for pregnant women and young children, including pneumonia, neurological impairment, hearing loss and death.