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. Cases in Gaines County,

Texas health officials reported 663 measles cases in the state on Tuesday, accounting for the majority of cases across the U.S., which reached nearly 900 as of Friday, according to the Centers for Disease Control and Prevention.

Nearly all measles infections seen during the Texas outbreak are among individuals who have not been vaccinated, or whose vaccination status is unknown.