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.

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.

Texas' measles outbreak is up to 90 cases. Here's what you need to know about the virus, vaccination and boosters.