Naegleria fowleri is a free-living microscopic ameba belonging to the phylum Percolozoa. It can be pathogenic, causing a fulminant (sudden and severe) and fatal brain infection called naegleriasis, also known as primary amoebic meningoencephalitis (PAM). This ameba is commonly found in warm freshwater (e.g. lakes, rivers, and hot springs) and soil. Naegleria fowleri usually infects people when contaminated water enters the body through the nose. Once the ameba enters the nose, it travels to the brain where it causes PAM.