The measles outbreak that began in Texas before spreading to at least two other states swelled to 355 confirmed cases on Friday — and officials say there is no sign it’s slowing.

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.

But there's a silver lining, officials say: More people have received a measles, mumps and rubella vaccination this year in Texas and New Mexico, which also has an outbreak, compared to last year — even if it's not as high as they would like. And pharmacies across the U.S., especially in Texas, are seeing more demand for MMR shots.