NEW YORK (Reuters) – New York City Mayor Bill de Blasio declared a public health emergency in parts of Brooklyn on Tuesday in response to a measles outbreak, requiring unvaccinated people living in the affected areas to get the vaccine or face fines.

The city’s largest measles outbreak since 1991 has mainly been confined to the Orthodox Jewish community in Brooklyn’s Williamsburg, with 285 cases confirmed since October, de Blasio said at a news conference.

“This is the epicenter of a measles outbreak that is very, very troubling and must be dealt with immediately,” de Blasio said.

The disease is easily spread and can be fatal, but there have been no confirmed deaths so far, officials said.

The outbreak is part of a broader resurgence in the United States, with 465 cases reported in 19 states so far this year, according to the U.S. Centers for Disease Control and Prevention.

Officials from New York City’s Department of Health will check vaccination records of anyone who has been in contact with infected patients in certain parts of Brooklyn, officials said.

Those who have not received the measles-mumps-rubella vaccine, or can otherwise give evidence of immunity, such as having previously had the measles, will face a fine of up to $1,000.

(Reporting by Jonathan Allen and Gine Cherelus; Editing by Bill Berkrot)