Most of the measles cases are still among school-aged children in Gaines County, Texas health officials said Friday.

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.

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.