"This worries me and I want to do everything possible to prevent measles from getting a foothold in the United States and becoming endemic again," Schuchat said during a briefing with reporters on Thursday.
Most of the people who contract measles have not been vaccinated, according to the CDC.
Officials believe the outbreak is linked to someone with measles visiting Disney theme parks in California in December.
That state has been hit the hardest by this outbreak, with the California Department of Public Health reporting 91 cases there so far this year. In Arizona, meanwhile, more than 1,000 people -- a fifth of them children -- are being monitored for potential exposure.