State health officials said Friday in a news release that those who are infected are either unvaccinated or their vaccination status is unknown. Thirteen people have been hospitalized.

The cases have been concentrated in a “close-knit, undervaccinated” Mennonite community, Texas Department of State Health Services spokesperson Lara Anton said. Gaines County is highly rural, so many of the families send their children to small private schools or are homeschooled, Anton said.

“The church isn’t the reason that they’re not vaccinated,” Anton said. “It’s all personal choice and you can do whatever you want. It’s just that the community doesn’t go and get regular health care.”