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.

But the spread has led to more measles, mumps and rubella vaccination in Texas and New Mexico this year. Pharmacies in West Texas are also seeing an increase in demand for the shots.

Three hundred and fifty-five cases have been reported in the ongoing measles outbreak in Texas, New Mexico and Oklahoma, but local officials say that it’s an undercount and that the virus could continue to spread spread for months.