Sources of Infection & Risk Factors

Three young adults jump into lake

Naegleria fowleri is a free-living ameba that causes primary amebic meningoencephalitis (PAM), a disease of the central nervous system.1, 2 PAM is a rare disease* that is almost always fatal. In the United States,** there have been 157 PAM infections from 1962 through 2022 with only four survivors. These infections have primarily occurred in southern-tier states, with almost half of all infections occurring in Texas and Florida. PAM also disproportionately affects males and children. The reason for this distribution pattern is unclear but may reflect the types of water activities (such as diving or watersports) that might be more common among young boys.3

For figures and tables representing information on cases of PAM that occurred from 1962 through 2022, visit Publications, Data, & Statistics.

  1. Marciano-Cabral F, Cabral G. The immune response to Naegleria fowleri amebae and pathogenesis of infection. FEMS Immunol Med Microbiol.2007;51:243-59.
  2. Visvesvara GS. Free-living amebae as opportunistic agents of human disease. J Neuroparasitol. 2010;1.
  3. Yoder JS, Eddy BA, Visvesvara GS, Capewell L, Beach MJ. The epidemiology of primary amoebic meningoencephalitis in the USA, 1962-2008. Epidemiol Infect. 2010;138:968-75.

*Rare Disease
There is no universal definition of a “rare disease” but the U.S. Rare Disease Act of 2002 defined a rare disease as affecting less than 200,000 people in the U.S. and this definition has been adopted by the National Institutes of Health, Genetic and Rare Diseases Information Centers.

**Including U.S. states, territories, and commonwealths.