A county in New York state has declared a state of emergency in a radical step to combat a measles outbreak mainly affecting the local Strictly Orthodox population.

Unvaccinated children in Rockland County will be banned for 30 days from public spaces such schools, shopping centres and synagogues beginning on Wednesday.

It is believed to be the first order of its kind in the United States.

“We must do everything in our power to end this outbreak and protect the health of those who cannot be vaccinated for medical reasons and that of children too young to be vaccinated,” county executive Ed Day said.

Rockland’s Strictly Orthodox Jewish communities have close ties to New York City, which is 40 kilometres to the south. The New York Times reported there are particularly close ties to Brooklyn, where vaccination rates tend to be lower and anti-vaccination literature has been distributed.

Mr Day said some members of the Rockland community had refused to answer health officials’ questions and even hung up the telephone.

Such “shockingly irresponsible” behaviour was justification for his order, he said.

Rockland County has had 153 confirmed cases of measles since October, of which 48 have occurred in 2019.

The United States formally eliminated measles in 2000, but there have been a number of outbreaks in recent years.

In London, a measles outbreak in the Strictly Orthodox community late last year led to more than 500 children receiving emergency vaccinations.

The outbreak in Stamford Hill was believed to have been triggered by carriers returning from Israel, where politicians have proposed stricter penalties for parents who fail to vaccinate their children.