Gaines County is a vast, flat expanse far in the west of Texas: more than 1,500 square miles of sparsely populated farmland. And right now, this is the epicenter of a measles outbreak the likes of which this state hasn’t seen in more than 30 years.

The Mennonite population being affected by a measles outbreak in West Texas is part of a larger, loosely affiliated group of churches worldwide with varied beliefs and leadership structures — and with sometimes strained or distant relations with health officials and other public authorities.