Dr. Ana Montanez is working overtime in Lubbock to contact vaccine-hesitant parents, explaining the grave risks posed by a disease that most American families have never seen, and one that can be prevented through immunization.

Cases in the ongoing measles outbreak have risen to 258 across Texas, New Mexico and Oklahoma, and state health departments are urging more people to get the measles-mumps-rubella vaccine.

In Texas specifically, a total of 223 people have contracted measles since the outbreak began in January, with at least 29 people, mostly children, requiring hospitalization. One child, who was unvaccinated, has died from measles, while a second unvaccinated person’s death is currently being investigated by health officials.