NEW YORK, United States (AFP) — New York Mayor Bill de Blasio declared a public health emergency in parts of Brooklyn on Tuesday, ordering all residents to be vaccinated to contain 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 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 US$1,000, said a statement from the mayor’s office.

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 continue to take in unvaccinated students.

Like most American states — all but three, including California — 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. 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 the statement. 

“There’s no question that vaccines are safe, effective and life-saving.” 

Although measles was declared officially eliminated from the United States in 2000, outbreaks have occurred in five states this year, according to the Centers for Disease Control and Prevention (CDC).

The resurgence of the once-eradicated, highly-contagious disease is linked to a growing anti-vaccine movement in richer nations — which the World Health Organization has identified as a major global health threat.

Most of the New York cases involved unvaccinated or incompletely vaccinated individuals, according to De Blasio’s office.

The so-called anti-vax, or anti-vaxxer phenomenon has adherents across Western nations but is particularly high profile in the US, where it has been fueled by disinformation on social media.

Many vaccine opponents believe medically baseless claims that inoculations can cause autism and other negative health effects.

Experts insist vaccines are safe and necessary to protect the larger community from highly infectious diseases like measles, which can cause severe diarrhea, pneumonia and vision loss and can be fatal in some cases.