(NAN)New York’s mayor declared a public health emergency in parts of Brooklyn on Tuesday, ordering all residents to be vaccinated to fight a measles outbreak concentrated in the ultra-Orthodox Jewish community.

The order concerns all people living or working in four zip codes of Williamsburg, northwest Brooklyn, where some residents oppose vaccines on religious grounds — although neither Jewish texts nor local Jewish authorities advise against vaccination.

“It was time to take a more muscular approach,” de Mayor Bill de Blasio told a news conference as the emergency measures were announced.

“This can be turned around quickly,” he said. “We can stop this.”

Under the new rules, anyone who has not received the measles-mumps-rubella (MMR) vaccine or does not have evidence of immunity risks a fine of $1,000.

The city also warned that yeshiva religious schools and day care programs serving the local Orthodox Jewish community would face penalties and possible closure if they keep taking in students who are not vaccinated against measles, which can cause severe diarrhoea, pneumonia and vision loss and can potentially be fatal.

Like all but three American states, New York requires a series of vaccinations for school-age children but has until now granted exemptions on both medical and religious grounds.

Since October, however, 285 cases of measles have been confirmed in New York City, according to the Centers for Disease Control and Prevention (CDC). None proved fatal, but 21 patients required hospitalisation and five were admitted to intensive care.

“I urge everyone, especially those in affected areas, to get their MMR vaccines to protect their children, families and communities,” de Blasio said in a statement.