Confirmed U.S. measles cases broke 1,000 in the second week of May, surpassing last year's total by nearly four times.

The number of measles cases in the United States has crossed 1,000 for the first time in five years, federal data showed on Friday, as the country battles one of its worst outbreaks of the childhood disease.

The US has confirmed 1,001 measles cases since the outbreak began in January, even as the virus’ spread in the hardest-hit state has slowed.