An outbreak of measles in northwest Texas grew to 159 cases on Tuesday, about a dozen more than health officials reported late last week. The latest update from the Texas Department of State Health Services shows the outbreak remains concentrated in school-aged children who have not received the vaccine that protects against measles,

Measles has been spreading across the U.S. for the last several weeks, sickening people in at least nine states amid a growing outbreak in western Texas. Several people have been hospitalized and at least one unvaccinated school-aged child in Texas has died,