The measles outbreak first reported in Gaines County, Texas, has doubled to 48 cases since a count released earlier this week, the Texas Department of State Health Services said Friday. The first two cases were identified in late January and the numbers have been rising since.

Additional measles cases "are likely to occur" as an outbreak of the virus grows, the Texas Department of State Health Services said in its latest update.

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.