Health authorities warned of further spread. Most U.S. measles cases this year involved people 19 and under and those without a confirmed vaccination.

Texas reported 90 cases this week, while New Mexico reported nine. A majority of the cases have been in a Texas county where vaccination rates have lagged behind the rest of the state.

The measles outbreak in rural West Texas has grown to 90 cases across seven counties, the state health department posted online Friday, and 16 people are hospitalized. State health officials have said this outbreak is Texas’ largest in nearly 30 years.