The measles outbreak first reported in Gaines County, Texas, has doubled to 48 cases in the last four days, the Texas Department of State Health Services said in a statement 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.

The outbreak in Gaines County, with a population of about 22,000, has grown since two cases were reported in January. All those who contracted measles were unvaccinated, health officials said.