The parents of a Texas child who died from measles called the disease “good for the body” while touting alternative remedies — but an expert tells PEOPLE measles can put children "in grave danger" and emphasizes that deaths are "highly preventable.

The Texas parents, members of a Mennonite community, say the death of their 6-year-old daughter has not changed their stance against the measles vaccine.

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.

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.