New Mexico health officials announced that the measles outbreak has reached a third county in the state’s southeastern corner Tuesday.

An unvaccinated child in Chaves County, NM has been diagnosed with measles, marking the third county in New Mexico affected by the ongoing outbreak.

A second child has died in Texas after contracting measles, The New York Times first reported Sunday—the second confirmed death from the disease in a decade—as more than 600 measles cases have now been confirmed in 20 states, with much of the outbreak centered in northwest Texas.