A rare "brain-eating amoeba" has been discovered in recreational waters at several western national parks, including Lake Mead, Grand Teton, and Yellowstone. Researchers identified Naegleria fowleri, a one-celled organism that can cause a fatal brain infection, after surveying 40 thermally impacted recreational waters across five national parks and recreation areas in the western United States.
Study Findings
The study, published by the U.S. Geological Survey (USGS) and partner agencies, involved 185 samples taken from Yellowstone National Park, Grand Teton National Park, Olympic National Park, Newberry National Volcanic Monument, and Lake Mead National Recreation Area. Scientists found Naegleria fowleri in about one-third of the samples, specifically those from Lake Mead, Grand Teton, and Yellowstone.
What Is Naegleria fowleri?
Naegleria fowleri thrives in warm freshwater lakes, rivers, and hot springs. It is often called the "brain-eating amoeba" because it can cause primary amebic meningoencephalitis (PAM), a rare but almost always fatal infection. According to the study, brain infections caused by this amoeba have a 98 percent fatality rate.
Rarity and Risk
Typically, fewer than 10 people contract PAM in the U.S. each year, according to the Centers for Disease Control and Prevention (CDC). However, nearly everyone who gets PAM dies. From 1962 to 2024, the U.S. has seen 167 cases of PAM, with only four survivors.
Researchers wrote, "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." They encouraged broadening surveillance of N. fowleri, as warming global temperatures are likely to expand its geographic range.
The Independent has contacted USGS and the National Park Service for comment.
