An adult who was infected with measles has died in New Mexico, though the virus has not been confirmed as the cause. State health officials announced the death Thursday.

Texas and New Mexico on Friday reported an additional 59 cases of measles for a total of 228 known infections in those states, where an outbreak that began in West Texas in late January has spread, causing the first U.

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.