Of the more than 35 species of Naegleria that have been identified, only one species, N. fowleri, has been associated with human disease. The species was named after Malcolm Fowler who identified trophozoites of Naegleria in the olfactory bulbs and frontal lobes of the first reported human case in South Australia in 1965.
N. fowleri causes a disease called primary amoebic meningoencephalitis (PAM). From 1962 to 2015 there have been 135 documented cases of PAM in the United States with only three known survivors. While the majority of cases have primarily occurred in the Southern part of the United States (see map), cases have been reported as far north as Minnesota. N. fowleri is naturally found in warm (30° C - 46° C) freshwater such as ponds, lakes, and rivers, but has also been found in minimally chlorinated swimming pools, geothermal heated water such as hot springs and discharge from industrial or power plants, plus tap water. People cannot become infected by drinking contaminated water since the amoebae are killed by stomach acids. Cases occurring from tap water resulted from its use in nasal cleansing. The organism is not found in sea water and is sensitive to freezing.