The largest measles outbreak in Texas in more than 30 years showed no signs of slowing down on Friday, rising to 90 cases across seven counties. The increase represents a jump of more than 50% since the Department of State Health Services last released an update on Tuesday.

Health officials expect a measles outbreak in West Texas to exceed 100 cases because of low vaccine rates and undetected infections. Vaccine misinformation and new laws may make such situations more common and harder to contain.

The ongoing Texas measles outbreak has rapidly grown to the largest the state has seen in decades, spreading through mostly unvaccinated residents and creeping across both county and state lines. On Friday morning,