An outbreak of measles has spread to 48 cases across four counties in the South Plains region of northwestern Texas, doubling in scope from earlier this week, health officials said. Most of the cases are in school-aged children,

Most of the infections have shown up in Gaines County. Texas health officials have consistently said that vaccination is the best way for people to avoid the highly contagious airborne disease.

At least 49 cases have been confirmed. Health officials — who are scrambling to get a handle on the vaccine-preventable outbreak — suspect 200 to 300 people may be infected.