People become infected when water containing Naegleria fowleri enters the nose and the ameba migrates to the brain along the olfactory nerve. People do not become infected from drinking contaminated water. The infection is caused by the following modes of exposure:

Water Activities: Naegleria fowleri infection most commonly occurs when contaminated water enters the body through the nasal passages. Activities that can lead to exposure include swimming, diving, water sports, or even using contaminated water for nasal irrigation or sinus rinsing.