An outbreak of measles has struck the South Plains region of Texas, with 90 cases reported since late January, according to the Texas Department of State Health Services (DSHS). The outbreak has affected seven counties in total,

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.

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.