The measles outbreak in Texas has escalated sharply to 90 cases as health officials worry about the spread to more communities.

A measles outbreak in Texas’ South Plains neared 100 cases Friday, according to the Texas Department of State Health Services, which warned more cases of the highly contagious virus are likely to pop up in outbreak areas.

A fast-growing measles outbreak in West Texas has nearly doubled in just one week, now totaling 90 cases across seven counties and spreading to New Mexico. Earlier this week, the Texas Department of State Health Services confirmed 49 cases in five counties.