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NOTE: A surveillance case definition is a set of uniform criteria used to define a disease for public health surveillance. Surveillance case definitions enable public health officials to classify and count cases consistently across reporting jurisdictions. Surveillance case definitions are not intended to be used by healthcare providers for making a clinical diagnosis or determining how to meet an individual patient’s health needs.

Subtype(s)

  • Free-living amebae infections
  • Acanthamoeba disease (excluding keratitis)
  • Acanthamoeba keratitis
  • Balamuthia mandrillaris disease

Clinical Description

N. 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 Criteria For Diagnosis

Laboratory-confirmed N. fowleri infection is defined as the detection of N. fowleri

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

Subtype(s) Case Definition

Case Classification

Confirmed

A clinically compatible illness that is laboratory confirmed.*

Comments

N. 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.

Related Case Definition(s)