The Texas health department reported 663 cases of measles in the state on Tuesday, an increase of 17 cases since April 25, as the U.S. battles one of its worst outbreaks of the childhood disease.

Of those infected across the U.S., 97% of cases came from those who are unvaccinated or whose vaccination status is unknown.

The number of cases reported in Texas’ historic measles outbreak has risen to 597, an increase of 36 cases since Friday, according to state officials on Friday. Of those, 62