Texas' measles outbreak is now at 90 cases, the highest yearly case count since 1992. Experts say the number is likely to grow more. Here's why.

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.

Lea County, New Mexico, is now reporting an outbreak of measles, according to the New Mexico Department of Health (NMDOH). Lea County is near Gaines County, Texas, where measles cases continue to rise as part of the original outbreak.