NEW YORK (REUTERS) - A Brooklyn judge on Thursday (April 18) denied a petition seeking to lift New York City's recently-imposed mandatory measles vaccination order, dismissing a court challenge brought by an anonymous group of parents who argued the order was unconstitutional.

The judge sided with municipal health authorities who issued the order last week, calling it a rare but necessary step to contain the worst measles outbreak to hit the city since 1991.

The outbreak has infected at least 329 people so far, most of them children from Orthodox Jewish communities in the borough of Brooklyn.

(This story is developing)