Texas health data released Friday shows an outbreak of measles in the West Texas region has surged to 597 cases.

The Centers for Disease Control and Prevention reported 800 confirmed cases of measles in the U.S. as of Friday, making the announcement as the highly contagious illness has reached half of the country—though most cases remain focused in Texas.

State health officials said fewer than 30 of the cases identified by the state were considered "actively infectious."