The U.S. declared measles eliminated in 2000 "thanks to a very high percentage of people receiving the safe and effective measles, mumps, and rubella vaccine," the CDC said, but now U.S. coverage among children of kindergarten age is below the 95 percent coverage target, which creates a higher risk for outbreaks of the virus.

A measles outbreak in Texas’ South Plains neared 100 cases Friday, according to the Texas Department of State Health Services, which warned more cases of the highly contagious virus are likely to pop up in outbreak areas.