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

The Texas health department reported 561 cases of measles in the state on Tuesday, an increase of 20 from April 11, as the U.S. government said it was sending seven people to the state to help battle the outbreak of the childhood disease.

The department said the outbreak is primarily in West Texas and added that 4% or fewer than 30 of the confirmed cases are estimated to be actively infectious since their rash onset date was less than a week ago.