The individual—whose name, age, and sex were not released by local authorities—is the second person to die from the virus amid a growing outbreak along the New Mexico-Texas border, sparking widespread concern among doctors that the federal government’s response is simply not enough to halt the spread of measles.

A measles outbreak in the American southwest has killed a second person, an unvaccinated adult, New Mexico health officials said on Thursday. The fatality comes roughly a week after measles took the life of an unvaccinated child in nearby Texas, the first US death from the disease since 2015.

A second person with measles died, but the official cause of death hasn’t been determined.