It's a record breaking year for measles cases in the United States.
So far, 288 cases have been confirmed, the most in 20 years. The resurgence comes after the disease had been officially eliminated from the country in 2000.
"Measles has reached a 20-year high. This is not the kind of record we want to break," Dr. Anne Schuchat, with the Centers for Disease Control and Prevention, said.
Experts say almost all cases have been linked to travelers who contracted the virus abroad then exposed unvaccinated people in the United States.
Many of the travelers had been to the Philippines, where a recent measles epidemic has caused more than 30,000 illnesses.