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How Scared Should I Be of Brain-Eating Amoebas?

Yes, it eats people's brains. No, it probably won't eat yours.

This week saw yet another of those horrifying and tragic news stories in which an otherwise healthy person dies suddenly from a disease straight out of bad science fiction. Something called a "brain-eating amoeba"—technically: Naegleria fowleri—sneaks into the victim's brain, usually while they innocently swim in a natural body of warm, fresh water or an under-chlorinated swimming pool. This time it was 19-year-old Kerry Stoutenburgh who spent a few days this summer enjoying the natural streams of Maryland. Stoutenburgh was a student at Brooklyn college, before she began showing symptoms of primary amebic meningoencephalitis, the fatal disease caused by Naegleria fowleri. She was taken off life support late last month. The intense brain eating amoeba coverage this year seems to dovetail with the trend The Verge clued me in to in 2013: Thanks to global warming, amoebas in the brains of Americans might be trending upward. Since I prefer my brain to be uneaten, and I like to know well ahead of time about potential plagues that could kill me, it seems like the perfect time to get some solid information about my risk.


Here's what I found out:

It's too soon to claim that cases are on the rise

In an interview back in 2013, Dr. Jennifer Cope, who tracks Naegleria fowleri for the Centers for Disease Control and Prevention, cautioned against jumping to the conclusion that cases were increasing. Now that it's been three years, I asked her for an update. She said the pattern still doesn't point to an increase, per se. "If you look at our numbers, we've had as few as zero, and as many as eight cases per year, and this summer we're at five infections," she told me in an interview.

But that doesn't mean we're out of the woods by any means. "We don't get those 'zero summers' any longer," she cautioned.

They only eat brains by accident

Left to its own devices, Naegleria fowleri could be called a "bacteria-eating amoeba," Cope explained. It floats around eating pond germs, with absolutely no interest in human brains. Traversing a human nostril, attaching to the olfactory nerve, and eating its way north is just an accident of nature, not an evil plan. But after that accident, this amoeba can't find the bacteria it's used to eating, and it starts doing exactly what the headlines say: "When it finds itself up someone's nose, it switches to the brain as its food source," Cope told me.

Worth noting for your anxiety: the term "brain-eating amoeba" can—and sometimes does—refer to Naegleri fowleri's somewhat more mysterious cousin Balamuthia mandrillaris, which is acquired from soil rather than swimming.


The disease is as awful as you've read

Once it gets situated, in as little as one day, things might taste or smell different on account of the amoebas chomping away at the inner workings of your nose. Over the next one to two weeks, symptoms will start to seem more like meningitis, because, as Cope reminded me, meningoencephalitis, meningitis, and encephalitis are all terms for inflammation in and around the brain, and the symptoms are similar.That means headache, stiff neck, nausea, and fever are all signs that you could have an amoeba problem.

As with most fatal forms of meningitis, it's not so much the loss of brain cells that kills you, but pressure, as the inflamed brain presses down on the connection between the brain stem and the spinal cord, eventually leading to coma, and respiratory failure. "We would suspect that the patients themselves are not very aware of what's happening in the later stages," Cope told me.

Your actual odds of infection are almost nil… almost

Despite all the amoeba coverage in the media, there were still only five cases in 2016. That's not many, Cope conceded. "There are 3,500 fatal drownings annually in the United States, and we can compare that to just a handful of Naegleria infections that get reported each year." The number cases is similar to the number of people killed by choking on balloons. And considering most water with Naegleria in it is in the south, it bears mentioning that many of those bodies of water are infested with alligators, which, y'know, can also be deadly.

"There are obviously many things that people should consider when they're participating in water activities," Cope said. I pressed her on whether I should worry about Naegleria more than other parasites I can get by swimming in warm, fresh water, for instance, the microscopic flatworms that cause "swimmer's itch," a common, temporary rash. "It certainly happens with more frequency than Naegleria infections do," she told me, "but the major difference is that you don't die from swimmer's itch," Cope said.


Another parasite that can kill American swimmers is Cryptosporidium. It's a fairly common cause of diarrhea—accounting for $45.8 million in hospital stays per year. But that parasite is extremely rare as a cause of death. Even in large outbreaks, it only appears to be associated with fatalities when patients' immune systems are compromised by something like HIV. Still, you're much more likely to get Cryptosporidium-related diarrhea from splashing around than a brain-eating amoeba.

Caution is really easy, assuming it helps

Since these amoebas mainly show up in warm, fresh water, mostly in the South, anything that gets referred to as a "swimmin' hole" should be treated with suspicion. But if you just have to plunge into any murky water as this summer winds down, the CDC has a few recommendations: Swimmers can either keep their faces dry, or just keep the water out of their noses, "by holding their noses, or using nose clips," Cope said. And until the weather cools off, it also might be smart to skip using a neti pot to irrigate your sinuses. That is if you're one of those weirdos who like pouring warm water up their noses.

But here's a final word of warning: The CDC actually has no idea if these preventative measures work. "That's a drawback to having so few infections: there's very little scientific study we can do," Cope said. Since it's not like the CDC can shoot amoeba water up people's noses for science, she said, "none of these things we recommend are things we can formally test."


So if you're planning on playing one last game of Marco Polo in a storm drain before the weather cools down, good luck not dying.

Final Verdict: How Scared Should I Be of the Brain-Eating Amoeba?

2/5: Taking Normal Precautions

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