Texas is now reporting 223 measles cases in the outbreak that began in Gaines County. There are dozens more cases in New Mexico, too.

As a measles outbreak has grown in Texas and New Mexico, doctors and public health experts have stressed that the measles, mumps and rubella vaccine is the most effective protection against the highly contagious respiratory virus.

A child’s death this past week in Texas is the first U.S. death from measles, a highly contagious but preventable respiratory disease since 2015, according to the U.S. Centers for Disease