Measles cases in Texas increased from 146 to 159 on Tuesday, a week after an unvaccinated child died of the disease in one of the largest outbreaks that U.S. has seen in the past decade.

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.