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Medical Author:

Mary D. Nettleman, MD, MS, MACP

Mary D. Nettleman, MD, MS, MACP

Mary D. Nettleman, MD, MS, MACP is the Chair of the Department of Medicine at Michigan State University. She is a graduate of Vanderbilt Medical School, and completed her residency in Internal Medicine and a fellowship in Infectious Diseases at Indiana University.

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Medical Editor:

Charles Patrick Davis, MD, PhD

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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In this Article

• Naegleria fowleri infection facts
• What is Naegleria fowleri?
• What causes a Naegleria fowleri infection?
• What are risk factors for Naegleria fowleri infection?
• What are symptoms and signs of a Naegleria fowleri infection?
• How is a Naegleria fowleri infection diagnosed?
• What is the treatment for a Naegleria fowleri infection?
• Can Naegleria fowleri infections be prevented?
• What is the prognosis of a Naegleria fowleri infection?
• Where can people find additional information about Naegleria fowleri infections?
• Naegleria Infection Index

N. fowleri is a water-borne disease. Exposure occurs when people come into contact with warm, fresh water usually through swimming, diving, water skiing, or other recreational activity. Although contact with infected water is common, symptomatic disease caused by N. fowleri is rare. It is common for people in the southern U.S. to have antibodies showing evidence of past exposure even when they have no history of symptoms or disease.

The danger of serious infection comes when water containing Naegleria fowleri is forced in into the nose and nasal mucosa. The parasite then migrates through the olfactory nerves and enters the brain. The initial step of infection can occur when diving or inadvertently aspirating water during swimming. Rarely, under-chlorinated swimming pools have been implicated in transmission. Because Naegleria fowleri can be present in untreated well water, there is a small but real chance of transmission to young children during bathing. Naegleria fowleri has also caused disease in adults who inject water into the nose as part of ritual ablutions related to religious practices.

The major risk factor for infection is recreational exposure to warm fresh water, especially if there is a history of aspiration of water into the nose. A review of cases in the U.S. by Yoder, et al. showed that there were 111 reported cases of primary amoebic encephalitis between 1962 and 2008. Living in the southern States is a risk factor for infection, because the water is warmer and more conducive to growth of the amoeba. A frequently asked question is when infections most commonly occur. The answer is that the organism is most active in summer months, even in the southern states. Most cases occur in previously healthy young males (median age of 12 years).