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 intensified to 309 cases with 40 hospitalizations. HOUSTON — A measles outbreak in Texas has intensified, with the Texas Department of State Health Services now confirming 309 cases statewide since late January — up from 279 cases reported earlier this week.

Vaccination efforts have faltered, and many residents have turned to alternative treatments endorsed by Robert F. Kennedy Jr., the health secretary.