A measles outbreak in West Texas has sickened at least 198 people, with 23 patients hospitalized and one dead.

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.

Texas’ health commissioner told lawmakers Monday they are still trying to determine the origin of a South Plains-Panhandle measles outbreak more than a month after the first patients reported symptoms.