A measles outbreak in Kansas has more than doubled to nearly two dozen cases over the last week, according to state health officials, who said they identified a “possible link” between confirmed cases of the highly contagious illness and a larger outbreak in Texas and New Mexico.

State health officials worry that declining vaccination rates have left many communities vulnerable nationwide.

Measles outbreaks in West Texas and New Mexico now have 370 cases in total. Two unvaccinated people have died from measles-related causes.