Q: When did the Centers for Disease Control and Prevention declare measles eradicated? I’m under the impression it was in 2000. Why is there is another outbreak?

—David Williams, Dawsonville

A: The U.S. declared in 2000 that measles had been eradicated from this country through a "highly effective measles vaccine, a strong vaccination program that achieves high vaccine coverage in children and a strong public health system for detecting and responding to measles cases and outbreaks," the CDC states on its website.

Unvaccinated people who are infected in other countries can spread measles to other unvaccinated people when they visit the U.S. The largest measles outbreak worldwide last year occurred in the Philippines, where there were 57,564 suspected cases, 21,403 confirmed cases and 110 deaths from Jan. 1 through Dec. 20, the World Health Organization reported.

No source has been identified in this year’s Disneyland outbreak, which has affected more than 100 people. Last year’s measles outbreak in Ohio was tracked to unvaccinated Amish missionaries who returned from the Philippines and spread the disease to 383 people. Of the 644 measles cases reported in the U.S. in 2014, that outbreak represented more than half, the Associated Press reported. It was the worst year for measles in this country since 1994.

There were 121 reported measles cases in 17 states and the District of Columbia as of Feb. 6, the CDC reported, a list that doesn’t include Georgia, which reported its first case since 2012 earlier this week.

Andy Johnston wrote this column. Do you have a question about the news? We’ll try to get the answer. Call 404-222-2002 or email q&a@ajc.com (include name, phone and city).