A historic measles outbreak in West Texas is just short of 200 cases, Texas state health officials said Friday, while the number of cases in neighboring New Mexico tripled to 30. Most of the cases across both states are in people younger than 18 and people who are unvaccinated or have an unknown vaccination status.

Nearly 230 measles cases have been identified in outbreaks in West Texas and a nearby county in New Mexico. Experts say the rising totals – and two recent deaths – suggest that cases are vastly undercounted.