Gaines County in West Texas is at the heart of the ongoing measles outbreak. Non-medical vaccine exemption rates there are high.

The effectiveness of the vaccine, coupled with rising vaccination rates, led to such low rates of measles that it was declared eliminated in the U.S. in 2000. In recent years, though, the virus has made a resurgence, as childhood vaccination rates have dropped nationwide.

A child in West Texas has died of measles, state health officials said on Wednesday, the first reported U.S. death from the highly contagious disease in a decade, as a Texas outbreak has grown from a handful of cases to more than 130 across two states.