Brain-Eating Amoeba Detected in Western National Park Hot Springs, Prompting Health Warnings

A new Outside study finds Naegleria fowleri, the brain-eating amoeba, in hot springs and thermally heated waters across western National Park Service sites including Yellowstone, Grand Teton, and Lake Mead Recreation Area. The amoeba was detected in 34% of samples, with some locations showing concentrations high enough to exceed public health limits. Infections are rare but typically fatal, occurring when the organism enters the nose and travels to the brain. As water warms with climate change, the amoeba’s range may expand, increasing exposure risk. Public health guidance emphasizes avoiding nasal exposure, using nose clips, keeping the head above water, and monitoring for symptoms. While not alarmist, authorities urge enhanced monitoring and awareness in thermally influenced recreational waters.