Mayor Bill de Blasio has declared a public health emergency amid an ongoing outbreak of measles in Brooklyn's ultra-Orthodox neighborhoods. According to health department officials, confirmed cases of the infectious disease in New York City have more than doubled in the last six weeks, and have now spread to at least 285 people since October, most of whom are children.

The emergency declaration will allow the city to compel residents of four Brooklyn zip codes — 11205, 11206, 11211, and 11249 — to receive the measles vaccination. The Department of Health and Mental Hygiene will be empowered to check vaccination records of individuals who have been in contact with infected patients, and to potentially levy fines of $1,000 on those who don't comply with the vaccination orders after three days.

"The measles vaccine works. It is safe, it is effective, it is time-tested," said the mayor during a news conference on Tuesday, before apologizing for his previous comments about there being a "debate" about vaccines (there is not).

Health officials on Tuesday also noted the jump in measles cases following the Jewish holiday of Purim, adding that they were concerned about a similar spike when Passover begins next week. "The outbreak could especially spread because soon it will be Passover and families will be together," de Blasio said. "So we are taking urgent steps right now to make sure we can stop this. It's not our goal to issue a violation. Whenever people comply promptly, we will not levy fines."

Details on how the fines will be collected remain vague, and city officials said they still needed to speak to attorneys about what happens if people continue to refuse the vaccinations after being fined. According to New York state law, children are required to be vaccinated to attend public and private schools, though parents are allowed to seek religious exemptions. In Rockland County, where there have been 168 confirmed measles cases since the fall, children without the vaccination were permitted to return to school yesterday, due to apparent confusion regarding a judge's ruling on the county's state of emergency.

During Tuesday's press conference, city authorities also said they'd learned of some parents bringing their children to "measles parties," where kids are intentionally exposed to the disease so that they might prove their immunization after recovering. "Getting vaccinated is far safer than getting the measles," assured Dr. Oxiris Barbot, the city's Health Commissioner.

Some ultra-Orthodox leaders came out in support of the mayor's order, including Rabbi David Niederman, head of United Jewish Organizations of North Brooklyn and Williamsburg. "We want every child to be vaccinated," he said. "People will learn how the Department of Health is committed and it will never get to fines because everybody is going to be vaccinated."

Even as city officials mount an increasingly aggressive campaign to stop the spread of measles, some members of the ultra-Orthodox community remain fiercely opposed to the vaccines. Citing advice from her spiritual advisor — who she declined to name — a woman named Ester told reporters on Tuesday that it was "completely ridiculous and unethical" for the city to "force me to inject something into my child's body." She added that all of her children have had measles.

But another woman passing by, Blimie Klien, 22, also a mother, said the vast majority of the community supports vaccination and would agree with the city's mandatory vaccination rule. "They are one percent, they're really a one percent," she said. "People are taking it very's because the mayor is saying it and because this is what our doctors are saying and we know we have to follow rules from our doctors."