U.S. health officials reported Monday that more people have contracted measles in the first three months of this year than they did in all of last year — a viral outbreak driven by unvaccinated children in various areas of the country two decades after the illness was declared eliminated.

The Centers for Disease Control and Prevention recorded 387 cases of measles through March, surpassing last year’s total of 372 cases. This year’s tally is the highest since 2014, when 667 cases were reported.

Four states — New York, Washington, New Jersey and California — have six outbreaks involving three or more cases, which are linked to travelers who have contracted the disease abroad in countries such as Israel, Ukraine and the Philippines, the CDC reported Monday.

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