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.

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.

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.