Policy & Recommendations

Naegleria fowleri is a free-living ameboflagellate that invades the brain and meninges via the nasal mucosa and olfactory nerve to cause acute, fulminant hemorrhagic meningoencephalitis (primary amebic meningoencephalitis – PAM), primarily in healthy children and young adults with a recent history of exposure to warm fresh water. Initial signs and symptoms of PAM begin 1 to 14 days after infection* and include sudden onset of headache, fever, nausea, vomiting, and stiff neck accompanied by positive Kernig’s and Brudzinski’s signs. In some cases, abnormalities in taste or smell, nasal obstruction and nasal discharge might be seen. Other symptoms might include photophobia, mental-state abnormalities, lethargy, dizziness, loss of balance, other visual disturbances, hallucinations, delirium, seizures, and coma. After the onset of symptoms, the disease progresses rapidly and usually results in death within 3 to 7 days. Although a variety of treatments have been shown to be active against amebae in vitro and have been used to treat infected persons, most infections have still been fatal.

Laboratory-confirmed Naegleria fowleri infection is defined as the detection of Naegleria fowleri:

1. Organisms in CSF, biopsy, or tissue specimens, or
2. Nucleic acid (e.g,. polymerase chain reaction) in CSF, biopsy, or tissue specimens, or
3. Antigen (e.g., direct fluorescent antibody) in CSF, biopsy, or tissue specimens.

*More recent analysis of the data indicate that signs and symptoms start 1 to 9 days (median 5 days) after water exposure.

Confirmed: a clinically compatible illness that is laboratory confirmed.**

** When available, molecular characterization should be documented (e.g., genotype).

Naegleria fowleri might cause clinically similar illness to bacterial meningitis, particularly in its early stages. Definitive diagnosis by a reference laboratory might be required. Unlike Balamuthia mandrillaris and Acanthamoeba spp., Naegleria fowleri is commonly found in CSF.

While this disease is not nationally notifiable, tracking Naegleria fowleri infections is useful for understanding disease trends, increasing healthcare provider awareness, expanding knowledge of important environmental factors, and informing public health action.