The mayor of New York City has declared a public health emergency following a severe measles outbreak in Brooklyn.

Mayor Bill De Blasio said the city was making vaccinations for measles, mumps, and rubella (MMR) mandatory after an outbreak infected the Orthodox Jewish community in certain parts of Williamsburg, Brooklyn.

The fine for failing to comply with the mandatory vaccination order is $1,000.

Since the measles outbreak started in October, there have been 285 reported cases in the Orthodox Jewish community. About 246 of those cases involved children and 21 people have been hospitalised.

"Measles is a dangerous, potentially deadly disease that can easily be prevented with vaccine," Deputy Mayor for Health and Human Services Dr Herminia Palacio said in a statement on Tuesday. "When people choose not to get their children vaccinated, they are putting their children and others - such as pregnant women, people on chemotherapy, and the elderly - at risk of contracting measles."

Polio: iron lungs, leg braces and vaccination Show all 8 1 /8 Polio: iron lungs, leg braces and vaccination Polio: iron lungs, leg braces and vaccination A hospitalised child suffering from polio shows off his biceps to a doctor in 1947 Getty Images Polio: iron lungs, leg braces and vaccination Children being given an oral vaccine for polio, known then as infantile paralysis, in Hull during the 1961 epidemic Rex Features Polio: iron lungs, leg braces and vaccination A boy suffering from polio being treated with a type of 'iron lung' in hospital. A nurse operates the equipment at the end of the bed which controls the flow of air pressure Getty Images Polio: iron lungs, leg braces and vaccination A woman sees her new born baby whilst lying inside an iron lung as part of her treatment for Polio Getty Images Polio: iron lungs, leg braces and vaccination Polio victim Margaret Dixon watching the opening matches of the 1957 Wimbledon championships from her invalid chair Rex Features Polio: iron lungs, leg braces and vaccination Young children polio patients doing physiotherapy exercises wearing calipers against their outside beds at Wingfield Nuffield Orthopaedic hospital in Oxfordshire Rex Features Polio: iron lungs, leg braces and vaccination A five year old polio victim walks into the outstretched arms of Doctor George Deaver, faculty member of the New York University College of Medicine, during a demonstration at the Institute of Rehabilitation and Physical Medicine Getty Images Polio: iron lungs, leg braces and vaccination 6 May 1956: First injections for children against polio at the Hendon clinic Getty Images

New York City officials also warned yeshiva schools in Brooklyn that they will be fined or shut down if they allow unvaccinated children to attend.

In December 2018, city officials ordered yeshiva schools to ban unvaccinated children. However, one school in Williamsburg did not follow the order, and as a result, it is has since been linked to more than 40 cases.

Local officials said the majority of Orthodox Jews in Williamsburg are vaccinated, but a small number of anti-vaxxers are allowing the outbreak to spread rapidly.