The Centers for Disease Control and Prevention reports 695 measles cases in 22 states.
"This is the greatest number of cases reported in the United States since measles was eliminated from this country in 2000," says a CDC statement issued late Wednesday.
The agency attributed the high number of cases primarily to a few large outbreaks — one in the state of Washington and two others in New York state. The New York outbreaks are among the largest and longest-lasting since 2000.
"The longer these outbreaks continue, the greater the chance measles will again get a sustained foothold in the United States," the CDC said.
Health and Human Services Secretary Alex Azar said in a statement that the rise in measles cases is "avoidable."
"Measles is not a harmless childhood illness, but a highly contagious, potentially life-threatening disease," he said. "We have the ability to safely protect our children and our communities. Vaccines are a safe, highly effective public health solution that can prevent this disease. The measles vaccines are among the most extensively studied medical products we have, and their safety has been firmly established over many years in some of the largest vaccine studies ever undertaken."
Azar said the CDC is prepared to support local public health departments in monitoring and responding to outbreaks.
The measles outbreaks were largely imported by unvaccinated travelers who were exposed to the disease in another country and then on their return to the U.S. exposed other unvaccinated people. If a community is highly vaccinated, then the outbreaks are minimal or don't happen at all.
"However, once measles is in an under-vaccinated community, it becomes difficult to control the spread of the disease," said the CDC.
One community in which there is a lot of misinformation about the measles/mumps/rubella vaccine is in New York. The CDC said some organizations there are deliberately spreading "inaccurate and misleading information about vaccines."
The states with reported cases of measles 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.
The CDC will release new numbers on the measles outbreaks on April 29 as part of its campaign to encourage the lifesaving benefits of childhood immunizations.