Measles is spreading rapidly in New York City — 94 more people have gotten sick this month. Elsewhere, the infection has killed more than 1,200 since October.

Drew Angerer/Getty ImagesPedestrians walk near the Yeshiva Kehilath Yakov School in the South Williamsburg neighbourhood, April 9, 2019 in the Brooklyn borough of New York City. New York City has ordered all yeshivas in a heavily Orthodox Jewish section of Brooklyn to exclude from classes all students who aren’t vaccinated against measles or face fines or possible closure.

Measles – an exceedingly contagious virus that can prompt a high fever, rashes, bumps, brain swelling, and even death – is spreading rapidly among unvaccinated populations around the globe.

Unvaccinated people everywhere from Brooklyn, New York to northern Madagascar are discovering just how pervasive and contagious the virus can be in the absence of vaccinations.

The World Health Organisation reports that global case counts are up 300% this year compared with this same time last year. In the US, the official 2019 case count as of Monday was 626 people, well above 2018’s total of 372 cases for the entire year.

“Measles is a very contagious disease,” Robert Amler, dean of New York Medical College and a former chief medical officer at the Centres for Disease Control and Prevention (CDC), told Business Insider. “Where there are susceptible populations – meaning people who are unvaccinated and who have not received natural immunity from an actual infection with the wild virus – where those populations are, the measles virus will find them.”

More than 300 measles cases recorded in New York City alone

The measles has hit children in Orthodox Jewish neighbourhoods of New York particularly hard this year. The New York City health department has logged334 measles cases in Brooklyn and Queens so far in 2019, and New York state has reported another 232 cases outside the city.

The alarming New York measles outbreaks follow another one in the Pacific Northwest that started in January and sickened at least 73 people, most of whom were unvaccinated kids under 10 years old. Another much smaller measles outbreak popped up in Baltimore earlier this month; overall, cases have been confirmed in 22 US states this year, according to the CDC.

Dr. Amesh Adalja at the Johns Hopkins Center for Health Security said these types of outbreaks were not such a regular occurrence in the US just a decade ago.

“In earlier eras, it was kind of the norm to be vaccinated. It wasn’t something that people questioned,” Adalja told Business Insider. “But in the wake of the false links to autism that occurred in the mid 1990s, that whole celebrity culture picking up these false stories, we ended up in this type of a mess.”

Read More: From autism risks to mercury poisoning, here are 10 lies anti-vaxxers are spreading about the measles vaccine

Measles outbreak brooklyn spreads fastSpencer Platt/Getty ImagesA sign warns people of measles in the ultra-Orthodox Jewish community in Williamsburg on April 10, 2019 in New York City.

In Madagascar, measles has killed at least 1,200 people since October

The measles is also sickening and killing babies and kids in unvaccinated corners of Madagascar, where more than 117,075 people have contracted the virus since October. The measles outbreak is the nation’s biggest ever, but it’s not happening because people are hesitant to vaccinate their kids; rather, it’s because they don’t have good access to vaccines or can’t afford them.

The WHO reports that at least 1,205 people in Madagascar have died from the measles in this outbreak so far.

“My child had been vaccinated and received the first injection, but he died because we didn’t have the means to go and get him the second injection,” Dada, a Malagasy fisherman, told Reuters through a translator. “I couldn’t afford to take him to the public hospital, so I took him to a quack to get the injection.”

The family’s heartbreak extends further: Dada’s sister, Pela Manty, also recently lost two of her children to the measles virus.

“We didn’t expect the fact that they were not vaccinated would kill them,” she said.

Some parents in Madagascar are now lining up to get their kids vaccinated. One dose of the measles vaccine is about 93% effective at preventing the measles, while the full course of two doses protects people 97% of the time.

While no measles deaths have been reported yet in the US this year, Amler says access to good medical care shouldn’t be the reason that anyone chooses to forgo their shots.

“Do you really want to put your child’s life on the line, in the hopes that your child will be saved by medical care?” he asked. “That seems like a rather backward argument to say ‘it’s ok for my child to get measles because she is less likely to die.’ I would like a 0% chance of dying from the measles, particularly since measles can be prevented.”

Who should get a measles shot, and who should not

Most people born after 1956 should make sure they’re up to date on their measles shots. People born before January 1, 1957 are considered naturally immune because they were almost certainly exposed to the virus in childhood, even if they don’t remember it.

The MMR shot (the standard measles, mumps, and rubella vaccine) is normally administered to kids before they turn 7. An extra dose won’t do any harm for people who already have some measles immunity, so if you can’t confirm that you’ve gotten both doses of the measles vaccine, it is fine to get another.

But the measles vaccine is not for everyone.

Pregnant women, babies under 6 months old, and people with fragile immune systems like cancer and HIV patients should not get the vaccine. These people instead rely on others to get their shots so that herd immunity makes it hard for measles to spread among a community. (Remember: if just one person has the measles, 90% of the unprotected people around them will get it.)

In the US today, Amler said, part of the reason that more people are skipping vaccines is because some younger caregivers aren’t actively scared of near-eradicated contagious illnesses they have never seen before, like the measles. That was not the case one or two generations ago, when parents easily remembered the crippling effects of a virus like the measles.

“When wild measles was raging and there was no available control, everybody – just about everybody born – would eventually get the measles,” Amler said. “The vast majority would survive, but it would leave a trail of deafness, of blindness, of chronic pneumonia, and in some cases – the brain swelling and the death.”

Some of these rare and debilitating side effects stay with kids throughout their lives.

“I would be the last one to make my fellow citizens afraid,” Amler added. “I don’t think that’s a very ethical thing to do. But the reality is that in the absence of vaccination, measles does and will return. And with inadequate vaccine coverage in a population, it places all of us at risk.”

This story was originally published on April 17, 2019. It has been updated to reflect the growing measles case counts across the US.

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