Boiling River, Yellowstone National Park

OutsideMay 6

A 2026 study confirms Naegleria fowleri in popular national park hot springs and lakes. Here is what soakers need to know to stay safe.

Hydrothermal water mixes with river, amoeba detected.

12 sights in this story

Grand TetonSightA visit to this northwestern Wyoming park, which is as thrilling for wildlife watchers as it is for climbers, hikers,…
Polecate Hot SpringsSightContained highest concentration of N. fowleri.
Boiling RiverSightHydrothermal water mixes with river, amoeba detected.
Lewis LakeSightMultiple springs on southern shore tested positive.
Lake Mead Recreation AreaSight
Huckleberry Hot SpringsSight
Granite Hot SpringsSight
Goose LakeSight
Firehole Canyon Swimming AreaSight
Roger's Hot SpringsSight
Boy ScoutSight
Blue PointSight

Boiling River