Yes, you read that right: Brain-eating amoeba have been found in two popular U.S. national parks, according to a recent study from the U.S. Geological Survey, and a number of other institutions, published in the American Chemical Society’s journal, ES&T Water.
Here’s what to know.
What happened?
Researchers took 185 water samples from five popular U.S. national parks and looked at “40 thermally impacted recreational waters” at Yellowstone National Park, Grand Teton National Park, Lake Mead National Recreation Area, Olympic National Park, and Newberry National Volcanic Monument over an eight year period from 2016 to 2024.
What they found revealed widespread detection of Naegleria fowleri dubbed “brain eating amoeba” in 34% of the samples, or 63 specimens, at Yellowstone, Lake Mead, and Grand Teton hot springs and thermally impacted waters; however, they did not find it at Olympic National Park, or Newberry National Volcanic Monument.
It’s important to note that no infections or deaths have been reported at the sites due to the so-called “brain eating amoeba.”
What is Naegleria fowleri?
Naegleria fowleri is a free-living ameba, a one-celled organism that thrives in warm freshwater lakes, rivers, and hot springs, called the “brain eating amoeba” because it can infect and destroy brain tissue, according to the Centers for Disease Control and Prevention (CDC). While brain infections caused by Naegleria fowleri are quite rare, they are nearly always fatal (at a rate of 98%.)
If water containing the amoeba goes up a person’s nose into the brain, it can cause an infection called primary amebic meningoencephalitis, or PAM. Typically, fewer than 10 people a year in the U.S. get PAM, however almost everyone who gets PAM dies from it, per the CDC. Out of 167 reported cases of PAM in the U.S. between 1962 to 2024, only four people survived.
Exposure risks
Brain infections caused by Naegleria fowleri usually occur after a person goes swimming or diving in a lake, river, or other fresh water in the summer after a prolonged period when it was hot, causing higher water temperatures, but lower water levels.
The CDC cautions you cannot contract the Naegleria fowleri infection simply by swallowing water containing the amoeba, nor can a person pass it to another person.
How to reduce the risk of contracting a Naegleria fowleri infection
Our friends at the CDC suggest people hold their nose or wear a nose clip if you are jumping (or diving) into fresh water; and to keep their head above water in hot springs. Don’t dig in shallow water because Naegleria fowleri is more likely to live there.
Signs and symptoms of a Naegleria fowleri infection
PAM progresses quickly with early symptoms that can include headache, fever, nausea, and vomiting, stiff neck, confusion, lack of attention to people and surroundings, loss of balance, and hallucinations.
Most people with PAM die within 18 days after experiencing initial symptoms, with many entering a coma and dying after 5 days, per the CDC.
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