New York Mayor Bill de Blasio declared a public health emergency Tuesday for parts of Brooklyn's Williamsburg section following a measles outbreak affecting the Orthodox Jewish community fueled by a growing movement against vaccinations.

Unvaccinated people living in designated ZIP codes who may have been exposed to measles will be required to receive the vaccine to protect others from the outbreak, the mayor said.

Measles is highly contagious, but the vaccination is considered 97% effective, according to the Centers for Disease Control and Prevention.

“There’s no question that vaccines are safe, effective and life-saving,” de Blasio said. “The bottom line is to recognize that this is something that has become even more urgent."

Health Commissioner Oxiris Barbot said the outbreak was being "driven by a small group of anti-vaxxers" in the targeted neighborhoods.

"They have been spreading dangerous misinformation based on fake science,” he said. “We stand with the majority of people in this community who have worked hard to protect their children and those at risk."

The outbreak began in October, but many of these new cases were confirmed in the past two months. The vast majority of cases are children under 18 – and most of these measles cases were unvaccinated or incompletely vaccinated people, health officials said.

Members of the City’s Department of Health and Mental Hygiene will check the vaccination records of people who may have been in contact with infected patients. Those who have not received the vaccine or do not have evidence of immunity may be given a violation and could be fined $1,000, the mayor said.

Barbot is concerned about measles outbreaks spreading as people travel for Passover, which begins in less than two weeks.

"We’ve seen a large increase in the number of people vaccinated in these neighborhoods, but as Passover approaches, we need to do all we can to ensure more people get the vaccine," Barbot said.

The primary symptoms from the disease include fever, runny nose, cough and a rash that can spread across the entire body. People who are immunocompromised can develop pneumonia, swelling of the brain or other serious symptoms. Measles can cause men to become sterile and pregnant women to deliver prematurely.

"It's not Ebola, but it's a serious disease," said Lisa David president of Public Health Solutions, a major public health nonprofit in the city. "It was a major achievement to eradicate it (in the U.S.) in 2000."

Measles was introduced into the community by someone who picked up the disease in Israel, which is dealing with its own outbreak, health officials said.

Ogbonnaya Omenka, an assistant professor at Butler University who has a doctorate in public health, says the New York outbreak shows that people shouldn't believe they are safe without a vaccination because almost everyone else around them was vaccinated.

"Herd immunity can only carry a community so far," he said. "This mandatory vaccination order is a bold step, (but) this measles outbreak is serious, both from health and statistical perspectives."

In February, the department expanded vaccination recommendations for providers serving the Orthodox Jewish community to include an early, extra dose of the vaccine for children ages 6 months to 11 months who live in Williamsburg and Borough Park.

"It does interconnect with the anti-vaxx movement that is not just in the community, it's national and it's causing lots of problems," de Blasio said Tuesday.

On Monday, the city Health Department issued formal orders to all yeshivas – Jewish schools – in Williamsburg to comply with the mandatory exclusion of unvaccinated children or face fines and possibly be shut down.

The emergency was declared one day after federal health officials reported that the number of measles cases recorded across the USA rose by almost 100 last week.

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The CDC said Monday that 465 cases have been confirmed in 19 states in 2019, the second-highest total since measles was declared eliminated in the USA almost two decades ago.

The surge has been fueled in part by the anti-vaccination movement – most people who contract measles have not been vaccinated, the CDC said. If one person has the disease, up to 90% of the people close to that person will become infected if they are not immune, the CDC warned.

The World Health Organization described the disease as a prominent cause of death among young children, despite the availability of an effective vaccine. More than 110,000 people, mostly children, died of measles worldwide in 2017.

The last U.S. measles death on record was in 2015.

Omenka lauded the "messaging approach" employed by New York.

"The threat was clearly defined, the susceptibility of individuals was presented," Omenka said. "Additionally, by pointing out that none of the reported cases had led to death, as opposed to cases in other countries, the public health threat was put in perspective."

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