Diagnosis, Clinical Course, and Treatment of Primary Amoebic Meningoencephalitis in the United States, 1937–2013

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Primary amoebic meningoencephalitis (PAM) is a rapidly progressing waterborne illness that predominately affects children and is nearly always fatal. PAM is caused by Naegleria fowleri, a free-living amoeba found in bodies of warm freshwater worldwide.


We reviewed exposure location, clinical signs and symptoms, diagnostic modalities, and treatment from confirmed cases of PAM diagnosed in the United States during 1937–2013. Patients were categorized into the early (ie, flu-like symptoms) or late (ie, central nervous system signs) group on the basis of presenting clinical characteristics. Here, we describe characteristics of the survivors and decedents.


The median age of the patients was 12 years (83% aged ≤18 years); males (76%) were predominately affected (N = 142). Most infections occurred in southern-tier states; however, 4 recent infections were acquired in northern states: Minnesota (2), Kansas (1), and Indiana (1). Most (72%) of the patients presented with central nervous system involvement. Cerebrospinal fluid analysis resembled bacterial meningitis with high opening pressures, elevated white blood cell counts with predominantly neutrophils (median, 2400 cells/μL [range, 5–26 000 cells/μL]), low glucose levels (median, 23 mg/dL [range, 1–92 mg/dL]), and elevated protein levels (median, 365 mg/dL [range, 24–1210 mg/dL]). Amoebas found in the cerebrospinal fluid were diagnostic, but PAM was diagnosed for only 27% of the patients before death. Imaging results were abnormal in approximately three-fourths of the patients but were not diagnostic for amoebic infection. Three patients in the United States survived.


To our knowledge, this is the first comprehensive clinical case series of PAM presented in the United States. PAM is a fatal illness with limited treatment success and is expanding into more northern regions. Clinicians who suspect that they have a patient with PAM should contact the US Centers for Disease Control and Prevention at 770–488–7100 (available 24 hours/day, 7 days/week) to discuss diagnostic testing and treatment options (see cdc.gov/naegleria).

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