Naegleria is an amoeba commonly found in warm freshwater and soil. Only one species of Naegleria infects people, Naegleria fowleri. Naegleria infects people by entering the body through the nose, often occurring when people use warm freshwater for activities like swimming or diving. The amoeba can cause a very rare but severe brain infection that is lethal in most cases. Click "source" to view the CDC's fact sheet.