A study published in ES&T Water found Naegleria fowleri, often called the “brain-eating amoeba,” in water samples from three of five recreation areas surveyed in the western U.S., including Yellowstone and Grand Teton national parks.
The study, conducted between 2016 and 2024 by researchers from the U.S. Geological Survey, Montana State University, and Australia’s Commonwealth Scientific and Industrial Research Organization, tested 185 samples from 40 thermally affected areas at Yellowstone National Park, Grand Teton National Park, Lake Mead National Recreation Area, Olympic National Park, and Newberry National Volcanic Monument.
Researchers detected Naegleria fowleri in 63 samples, or 34%. Olympic National Park in Washington and Newberry National Volcanic Monument in Oregon tested negative.
The organism was found in Yellowstone, Grand Teton, and Lake Mead. In Grand Teton, researchers reported a positive sample in 2019 at Granite Hot Spring, in the pool above the recreational area. At Lake Mead, four of five hot spring sample sites tested positive between 2018 and 2019: Blue Point, Boy Scout, Nevada, and Roger’s.
Naegleria fowleri lives in soil and warm freshwater, including lakes, rivers, ponds, and hot springs. According to the Centers for Disease Control and Prevention, infection can occur when contaminated water enters the nose and reaches the brain, causing primary amebic meningoencephalitis. Fewer than 10 people in the U.S. die each year from the infection, the agency said.
The CDC said 167 cases were reported in the U.S. between 1962 and 2024, and four people survived. Symptoms can begin with headache, fever, and nausea, then progress to confusion, seizures, coma, and death, often within seven to 10 days.
Researchers said in the study that Naegleria fowleri has moved northward since 1962 and that warming global temperatures may allow that trend to continue. They called for better monitoring, risk management, and public awareness.
