State health officials are seeking to confirm the vaccine status of the four self-reported cases, but no mutations of the virus have been recorded.

A measles outbreak in Texas has jumped from two cases among unvaccinated children to 48. With childhood vaccine hesitancy on the rise, outbreaks are increasingly likely.

At least three of the New Mexico cases are in Lea County, which borders Gaines County in Texas. The state health department has said people may have been exposed at a grocery store, an elementary school, a church, Nor-Lea Hospital and a Walgreens in Hobbs, New Mexico.