Texas health officials are warning residents and health care providers to stay alert after four cases of measles were confirmed in an unvaccinated Montgomery County family.

The Texas Department of State Health Services (DSHS) issued a health alert after the family members were infected by a person with measles who traveled to Texas from another state.

Because measles is one of the most contagious viruses, state health officials said additional cases could occur, particularly among people who are not vaccinated.