A health worker tests for measles at a mobile testing site in Texas in February. Case numbers are continuing to climb in Texas and a nearby New Mexico county. 
Julio Cortez/AP

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.

In the West Texas outbreak, 198 measles cases have been reported, the Texas Department of State Health Services said in an update Friday — 39 more confirmed cases since Tuesday’s update.

Also Friday, the New Mexico Department of Health reported 30 measles cases in Lea County, 20 more than had previously been identified in the state.

Health officials in both states said cases are expected to increase due to the highly contagious nature of measles.

In Texas, 23 patients have been hospitalized, one more than previously reported. Sixty-four cases are among people younger than 4, and 89 are among people 5 to 17. Cases have been identified in nine counties, but the majority, 137, are in Gaines County, where the outbreak was first identified.

Last month, Texas announced the outbreak’s first death, a school-age child who was not vaccinated, had no underlying conditions and had been hospitalized.

Health officials in New Mexico said Thursday that they are investigating the cause of death of an unvaccinated person who tested positive for measles. The Lea County resident had not sought health care.

Lea County borders Gaines County, but health officials said they have not confirmed a link between the Texas and New Mexico outbreaks.

Among the cases in New Mexico, 11 are in children 17 or younger, 15 are in people 18 and older, and four cases are pending.

The CDC issued a Health Alert Network advisory Friday to inform providers about the measles outbreaks in Texas and New Mexico and urge vaccination.

Measles-mumps-rubella (MMR) vaccination remains the most important tool for preventing measles. To prevent measles infection and spread from imported cases, all U.S. residents should be up to date on their MMR vaccinations, especially before traveling internationally, regardless of the destination,” the advisory reads.

One to three of 1,000 children who have measles will die from virus complications, according to the CDC.