Another 90 people in the US fell ill with measles in just one week, new Centers for Disease Control and Prevention data revealed Monday.
Now, there have been 555 cases of the once-eradicated disease in 2019, and le latest increase is the largest surge in cases seen in the ongoing outbreak yet.
It means that, despite declarations of states of emergency in both New York and Washington, the national measles outbreak is continuing to spread in 25 US states.
With another eight months to go this year, this year's measles outbreak could easily catch up to the record-setting 667 cases that stuck the US in 2014 as global cases have already surpassed the 100,000 mark.
Since January 1, the Centers for Disease Control and Prevention has confirmed 555 cases of measles in 25 states, new data revealed Monday
Measles was declared 'eradicated' in the US in 2000.
But the disease has since had a resurgence, with a record 667 cases in 2014 - and just four months into 2019, this year's tally is quickly catching up.
The highly infectious disease has been spreading among people who are unvaccinated or live in states that allow non-medical exemptions for vaccines.
Cases have been confirmed in: Arizona, California, Colorado, Connecticut, Florida, Georgia, Illinois, Indiana, Kentucky, Maryland, Massachusetts, Michigan, Missouri, Nevada, New Hampshire, New Jersey, New York, Oregon, Texas, and Washington.
Of those states, six - Arizona, Colorado, Michigan, Oregon, Texas and Washington - allow exemptions for philosophical and/or personal beliefs.
Washington and New York, particularly, have been struggling to contain the disease.
In January, Washington declared a public health emergency after a measles outbreak that has affected over 70 people in Clark County and one in King County, where Seattle is located.
Sixty-three of the cases are in residents who have not been vaccinated. Fifty-three cases are in children aged 10 and under.