Policy & Recommendations

Primary amebic meningoencephalitis (PAM) infection is not currently a nationally notifiable disease but is state reportable, as amebic encephalitis, in Florida 1, Texas 2, and Louisiana 3.

Although not formally a nationally notifiable disease, CDC informally tracks Naegleria fowleri infections with the voluntary assistance of state health departments. CDC has published a summary of all reported U.S. Naegleria fowleri infections from 1962 thru 2008 4.

CSTE Naegleria fowleri Case Definition

In 2011, the Council of State and Territorial Epidemiologists (CSTE) established a standard case definition for Naegleria fowleri infections 5.

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.

  1. Florida Department of Health. Disease Reporting and Surveillanceexternal icon 2016.
  2. Texas Department of State Health Services. Texas notifiable conditions 2016. pdf icon[PDF – 1 page]external icon 2016.
  3. Louisiana Department of Health and Hospitals. Sanitary code-State of Louisiana. Part II – The control of disease. pdf icon[PDF – 1 page]external icon
  4. Yoder JS, Eddy BA, Visvesvara GS, Capewell L, Beach MJ. The epidemiology of primary amoebic meningoencephalitis in the USA, 1962-2008.external icon Epidemiol Infect. 2010;138:968-75.
  5. Council for State and Territorial Epidemiologists (CSTE). Case definitions for non-notifiable infections caused by free-living amebae (Naegleria fowleri, Balamuthia mandrillaris, and Acanthamoeba spp.) pdf icon[PDF – 10 pages].external icon Infectious Disease Committee. 2012.