NEW YORK (Reuters) - The number of measles cases in the United States has reached a 25-year peak, propelled by the spread of misinformation about the vaccine that can prevent the disease, federal health officials said on Monday.

The U.S. Centers for Disease Control and Prevention reported 704 cases as of April 26, a 1.3 percent increase since the most recent tally of 695 reported on Wednesday. The vast majority of cases have occurred in children who have not received the measles-mumps-rubella vaccine, which confers immunity to the disease, officials said.

“The suffering we are seeing today is completely avoidable,” U.S. Health and Human Services Secretary Alex Azar said on Monday. “We know vaccines are safe because they’re among some of the most studied medical products we have.”

A vocal fringe of U.S. parents refuse to vaccinate their children believing, contrary to scientific evidence, that ingredients in them can cause autism.

Some 22 states have recorded cases of the extremely contagious and sometimes deadly disease. None of the victims of the recent outbreak have died, but 3 percent have contracted pneumonia and 9 percent have been hospitalized due to complications from the disease, CDC director Robert Redfield said on Monday.

U.S. President Donald Trump urged Americans last week to get vaccinated to prevent the spread of measles, changing course from remarks he made in 2014 when he expressed doubt about giving children government-recommended doses of vaccines.

“The vaccinations are so important. This is really going around now,” Trump said on Friday.

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The current outbreak has been concentrated in New York City, where officials said more than 390 cases have been recorded since October, mostly among children in Orthodox Jewish communities in Brooklyn. Most of the recently recorded cases have been in New York and Los Angeles, officials said on Monday.

The national outbreak has escalated since 82 people in 2018 and more than 40 people in 2019 brought measles to the United States from other countries, most frequently Ukraine, Israel and the Philippines, federal officials said.

Up to 10 percent of patients in the current outbreak are adults who had received one or two doses of the vaccine, the CDC said. Some adults may need a new dose depending on whether they received the recommended two doses of the live virus or if they are traveling into and out of outbreak areas.

Although the virus was eliminated from the country in 2000, meaning it was no longer continually present year round, outbreaks still happen via travelers coming from countries where measles is still common, the CDC says.