A rare but deadly amoeba, sometimes dubbed the "brain-eating amoeba," has been detected in recreational waters at several major western national parks and recreation areas in the United States.
The Independent reported that, according to a new study from the U.S. Geological Survey and partner agencies, researchers found Naegleria fowleri in thermally impacted waters at Lake Mead National Recreation Area, Grand Teton National Park, and Yellowstone National Park. The findings matter because the organism can cause a fast-moving brain infection that is almost always fatal.
The study surveyed 40 thermally influenced recreational waters across five western park sites: Lake Mead, Grand Teton, Yellowstone, Olympic National Park, and Newberry National Volcanic Monument.
Researchers collected 185 samples to identify the single-celled amoeba that lives in warm freshwater settings such as lakes, rivers, and hot springs.
Scientists reported Naegleria fowleri in roughly one-third of the samples. That makes the discovery especially notable for park visitors heading into warmer freshwater areas this season, even though infections remain extremely rare overall.
The amoeba can cause primary amebic meningoencephalitis, a severe brain infection. According to the study, the disease has a 98% fatality rate. The Independent noted that the Centers for Disease Control and Prevention data cited in the report said that fewer than 10 people in the United States get PAM each year, and almost all of them die from it.
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U.S. officials logged 167 PAM cases between 1962 and 2024, and four people survived. While the odds of infection remain very low, the consequences are so serious that even a small shift in where the organism appears can prompt concern among health officials and land managers.
The study also points to a broader concern: Researchers warned that warming global temperatures could help the amoeba spread into new geographic areas. Experts have also raised concerns about the flesh-eating Vibrio bacteria washing ashore on beaches in seaweed masses.
That could mean a bigger challenge for public agencies tasked with balancing recreation access, visitor education, and health protections in places people visit each year. More monitoring could become increasingly important as popular outdoor destinations face changing water conditions tied to rising temperatures.
"These findings indicate that N. fowleri is present in thermally impacted areas across the western United States and underscore the use of enhanced monitoring, public awareness, and risk management strategies in thermally influenced waters," the researchers wrote in the study, per The Independent. They also encouraged "broadening surveillance" of the amoeba as conditions continue to change.
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While there is good reason for heightened awareness, there is no need to panic.
"Infections remain extremely rare, and the study does not prompt any new nationwide warnings," a National Park Service spokesperson said in a statement, according to The Independent.
"Individual parks continuously evaluate local conditions and will issue visitor advisories or take appropriate management actions if circumstances warrant. Our focus remains on sharing practical steps visitors can take to reduce risk while enjoying the parks."
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