As measles cases in West Texas are still on the rise two months after the outbreak began, local public health officials say they expect the virus to keep spreading for at least several more months and that the official case number is likely an undercount.

The Texas measles outbreak has grown to a total of 327 cases, according to new data released Tuesday, March 25, up from 309 cases last week.

Measles cases in Texas and New Mexico rose to 370 on Friday, the health departments of the states said, an increase of 19 infections since their previous reports four days ago, as the United States deals with one of the largest measles outbreaks in the past decade.