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 measles vaccine has been proven to be safe and effective against the disease, which is highly contagious and can be life threatening.

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.

The number of measles cases associated with an outbreak in western Texas has grown to 309, according to new data released Friday.