Overview
- Researchers from the U.S. Geological Survey and Montana State University tested 185 samples from 40 recreational waters across five National Park Service sites and found Naegleria fowleri in 34% of them.
- Detections occurred in thermally influenced waters at Yellowstone, Grand Teton, and Lake Mead, including the Boiling River, Firehole River, Lewis Lake hot springs, Polecat and Huckleberry hot springs, and Blue Point, Boy Scout, Nevada, and Rogers hot springs.
- Olympic National Park and Newberry National Volcanic Monument showed no detections in the samples tested, underscoring how the amoeba clusters in warmer, hydrothermal areas.
- Polecat Hot Springs in Grand Teton reached 115.7 cells per liter in a 2023 sample, a level above France’s recreational-water guide of 100 cells per liter, while the U.S. has no concentration standards for this pathogen.
- The amoeba infects people when warm freshwater enters the nose and can cause primary amebic meningoencephalitis with a 98% fatality rate, yet cases remain rare in the U.S., leading researchers and park officials to urge expanded monitoring, clear signage, and public awareness at warm-water recreation sites.