Public health authorities said Tuesday that an outbreak of measles in western Texas has expanded, while a new case was confirmed nearby across state lines in New Mexico.

Two dozen cases of measles have been reported in a small West Texas county that has one of the state’s highest vaccine exemption rates. In Gaines County, which has a population of about 22,000, 24 cases of the airborne infectious disease have been reported since late January. Most of them are unvaccinated, school-aged children.

Authorities in the US states of Texas and New Mexico have reported that the outbreak of measles has expanded, with 10 new cases. According to the Texas Department of State Health Services, at least 24 measles cases have been identified in connection with the onset of symptoms within the last two weeks.