There have been more measles cases in the United States the first five months of 2019 than there were in all of 1992, when the last large outbreak occurred, federal health officials said on Thursday, in part because of the spread of misinformation about vaccines.

The Centers for Disease Control and Prevention said Thursday that there had been 971 known cases of measles in the United States so far this year.

That is eight more cases than in 1992, the previous high since vaccines became widely used, when 963 cases were reported in the United States all year. And it is a sharp jump from last year, when just 372 cases were reported, the center said. (Earlier Thursday, the C.D.C. mistakenly said that the previous high was in 1994.)

“Measles is preventable and the way to end this outbreak is to ensure that all children and adults who can get vaccinated, do get vaccinated,” Dr. Robert Redfield, the director of the C.D.C., said in a statement.

“Again, I want to reassure parents that vaccines are safe, they do not cause autism,” he added. “The greater danger is the disease that vaccination prevents.”

The center pointed to a continuing outbreak in New York City and Rockland County, N.Y., as posing a particular public health threat.

There had been 500 confirmed cases of measles in New York City since September 2018 as of May 29, the New York City Department of Health and Mental Hygiene said Thursday. Rockland County officials said 254 cases of measles had been reported there as of May 28.

Measles is a highly contagious virus that can cause serious respiratory symptoms, fever and rash, as well as permanent deafness or encephalitis in severe cases, according to the C.D.C.

The measles vaccine, which was first licensed in 1963 , is extremely safe and effective and causes no side effects in a majority of cases. Small numbers of people may experience a mild fever, rash, soreness or swelling after receiving the vaccine, and adults and teenagers may feel soreness or stiffness, according to the C.D.C.

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