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.

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

As the outbreak rages, unproven remedies like cod liver oil are being distributed free by some doctors. Families are lining up for them.