(JTA) — New York City Mayor Bill de Blasio declared a public health emergency on April 9 over the measles outbreak in Brooklyn’s haredi Orthodox community.

De Blasio ordered unvaccinated people living in four ZIP codes in the Williamsburg neighborhood to get the vaccine or be required to pay fines of up to $1,000.

There have been 285 reported cases of measles in Brooklyn’s Orthodox Jewish community since October, including 246 children, WCBS-TV reported, citing the health department.

The areas covered by the order are where most of the city’s measles cases have originated. They are largely populated by haredi Jews.

“This is the epicenter of a measles outbreak that is very, very troubling and must be dealt with immediately,” de Blasio said. “The measles vaccine works. It is safe, it is effective, it is time-tested … the faster everyone heeds the order, the faster we can lift it.”

“We cannot allow this dangerous disease to make a comeback here in New York City. We have to stop it now.”

The order comes a day after the New York City Department of Health threatened to fine or even close yeshivas in Williamsburg if students who are not vaccinated against measles are allowed to attend classes.

On Friday, a New York state judge lifted the state of emergency imposed by Rockland County that would have barred minors not vaccinated against the measles from public places.

The Brooklyn outbreak has been tied to an unvaccinated child who contracted the disease during a trip to Israel, The Washington Post reported.

Some 465 measles cases have been reported in 19 states this year, according to the U.S. Centers for Disease Control and Prevention.