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How a Deadly Brain-Eating Amoeba Could Spread Thanks to Climate Change

As the global climate warms, N. fowleri is moving north.
Rachel Pick
New York, US
The amoeba in its three biotic stages: cyst, trophozoite, flagellate. Image: CDC

A microorganism that feeds on human brain tissue sounds like something out of a horror movie or science fiction. But Naegleria fowleri is very real, and it seems to be spreading to new environments.

The amoeba likes warm, stagnant freshwater, and infection rates tend to go up in the summer months because of rising temperatures. Until recently US cases were limited to southern states, but global warming is poised to change that, as more bodies of water are becoming hospitable to the amoeba.

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N. fowleri, already responsible for the deaths of two Minnesota children in 2010 and 2012, has just killed another child in the state, a boy of 14. Another woman died earlier this month in California, the state's 7th recorded case in history.

The most recent death in Minnesota is now the northernmost case recorded in the United States, and some epidemiologists are concerned that cases might occur in more and more freshwater environments as the global climate warms.

A 2012 study examining the possible spread of N. fowleri reads, "Minnesota's temperature trends reveal an overall shift toward warmer climate for the state, with an increased rate of warming during the past 3 decades, compared with the rest of the 20th century." In the coming years, we may need to start taking better precautions on a national level.

Even if you don't really want to think about it, everyone knows deep down that bacteria and microorganisms are everywhere. The oceans are filthy. Chlorine doesn't kill everything lurking in swimming pools. Even the drinking water in New York City is full of microscopic shrimp called copepods. (And the subway? Fahgeddaboudit.)

But these tiny contaminants almost never cause us any harm, either because they're inherently innocuous or because of our body's natural defenses. Take N. fowleri, for example. If it enters your body through your mouth, it goes straight to your stomach and burns up in digestive acid. No harm, no fowleri.

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But if it goes up your nose, that's when you're in trouble.

It's rare, but that's when the amoeba could travel up your olfactory nerves to your brain, and begins to feed on your nerve tissue, piece by piece. The infection is called primary amoebic meningoencephalitis (PAM), and it eventually causes a nearly-always fatal swelling of the brain and its surrounding membrane.

The prognosis for these cases is bleak. Part of the problem is that the infection is initially hard to diagnose, and that onset can occur up to nine days after exposure, making it harder to trace the cause of a patient's symptoms.

The symptoms are routine at first. Fever, vomiting, headache—something that could easily be dismissed as the flu. But as the infection progresses, the patient begins to hallucinate and experience seizures. The current recommended treatment is miltefosine, an anti-cancer drug that is also used to treat leishmaniasis, another extremely deadly disease caused by a parasite. But in the rare event that a patient survives, it may just be due to luck. Death almost always occurs one to two weeks after symptoms develop.

Thankfully cases of PAM are rare, and the organism tends to grow only in certain environments that are easy to avoid, like lakes, ponds, and swimming holes. There are precautions you can take, like keeping your head above water or using nasal plugs. And even if you do go under in a contaminated body of water, your risk of infection is minimal.

But swimming in freshwater isn't the only thing that puts you at risk of infection, though it is the most common. If you engage in nasal irrigation (e.g. using a Neti pot), you should always boil your water first, or use water that's already been distilled. Two deaths in 2011 were attributed to people using bad water for nasal irrigation. In one of these cases, the infection was due to a faulty water heater running at a temperature too low to kill N. fowleri (but warm enough to keep it comfortable).

Despite the low level of risk, PAM is terrifying due to its mortality rate, which is over 97 percent in the US. So as temperatures rise and vacation season approaches, please, do us a favor and plug your nose.