Measles cases in the United States have now exceeded the highest number on record in a single year since the disease was eliminated in 2000.
Nationwide, at least 673 cases of the vaccine-preventable illness had been reported in 22 states this year, according to a preliminary tally of state and local health department data by the Washington Post.
That's more than the 667 cases reported in 2014, when one large outbreak primarily among unvaccinated people in Amish communities in Ohio accounted for more than half the total that year.
The outbreaks are linked to travellers who brought measles back from countries such as Israel, Ukraine and the Philippines, where large measles outbreaks are occurring.
This year, as in the past, officials say the majority of people in the US who have fallen ill were unvaccinated.
In some communities, anti-immunisation activists have spread false claims about the measles, mumps and rubella vaccine, causing concern among parents about innoculating their children.
When many people in a community have not been vaccinated, the disease can spread quickly. It is one of the most contagious diseases in the world and can cause serious complications, especially among young children, adults with weakened immune systems and the elderly.
The states that have reported cases to CDC this year are: Arizona, California, Colorado, Connecticut, Florida, Georgia, Illinois, Indiana, Iowa, Kentucky, Maryland, Massachusetts, Michigan, Missouri, Nevada, New Hampshire, New Jersey, New York, Oregon, Texas, Tennessee and Washington.