While most strains of Naegleria fowleri are harmless, one strain can cause a rare but deadly brain infection known as Primary Amebic Meningoencephalitis (PAM). This type of amoeba (micro-organism) is commonly found in warm freshwater bodies such as lakes, rivers, hot springs, ponds and is occasionally found in soil and poorly maintained swimming pools.
PAM is caused when Naegleria fowleri enters the body through the nose, usually when someone dives or jumps into warm freshwater. The amoeba then travels up the olfactory nerve and into the brain, where it begins to destroy brain tissue. Symptoms of PAM typically appear within a few days of infection and include headache, fever, nausea, vomiting, seizures, and hallucinations. PAM is often fatal, with only a handful of known survivors.
Unfortunately, there is no rapid, standardized test to detect Naegleria fowleri in water. Recreational water users should assume that Naegleria fowleri may be present in warm freshwater and that there may be a low-level risk of infection when entering these waters.
Infections with Naegleria fowleri are rare (there have only been around 40 cases reported in the United States in the past decade), they occur mainly during the summer months of July, August, and September when it is hot for prolonged periods of time, which results in higher water temperatures and lower water levels. Infections increase during heat waves and Naegleria fowleri is less likely found as water temperatures decline.
When taking part in water-related activities in bodies of warm freshwater it is best to
▪ Avoid warm freshwater when the water temperature is high, and the water level is low.
▪ Avoid putting your head under the water.
▪ Hold your nose shut or use nose clips.
▪ Avoid digging or stirring up the sediment.
- Centers for Disease Control and Prevention (CDC). (2021). Naegleria fowleri – Amebic Encephalitis. Retrieved from https://www.cdc.gov/parasites/naegleria/index.html,
- G. S. (2010). Parasitic meningoencephalitis in humans and animals. In Handbook of clinical neurology (Vol. 96, pp. 55-69). Elsevier.
- Cope, J. R., Conrad, D. A., Cohen, N., Cotilla, M., DaSilva, A., Jackson, J., … & Yoder, J. (2018). Use of the novel therapeutic agent miltefosine for the treatment of primary amebic meningoencephalitis: report of 1 fatal and 1 surviving case. Clinical Infectious Diseases, 67(9), 1375-1378.
- Visvesvara, G. S., & Moura, H. (2007). Naegleria fowleri (Chaos chaos): the “brain-eating” amoeba. In Handbook of clinical neurology (Vol. 87, pp. 145-156). Elsevier.