by Tami Port MS

Created on: June 11, 2009   Last Updated: June 21, 2009

In the summer of 2007, there were several reported deaths from a microscopic brain-eating amoeba; the final victim of the summer, 14-year-old Aaron Evans. Doctors believe that the teen encountered the microbe a week earlier while swimming in the warm, shallow waters of Lake Havasu in Western Arizona.

*Deadly Amoeba*

The culprit was Naegleria fowleri (nuh-GLEER-ee-uh FOWL'-erh-eye), a parasitic amoeba that enters the body through the nose and travels to the brain where it feeds on brain tissue, causing primary amoebic meningoencephalitis. There is no treatment for this infection, and it is nearly always fatal.

*How Common Is Amoebic Meningoencephalitis?*

Infection with the Naegleria amoeba is very rare. In the summer of 2007, there were six U.S. cases, all young men. A total of twenty-three infections were documented in the U.S. between 1995 and 2004. Infection most often occurs during the dry, hot summer months, when water is warm and at low levels. The number of infections tend to increase during years marked by heat waves.

*How Naegleria Attacks*

Infection occurs when the amoeba enters the body through the nose, invading the central nervous system by penetrating the olfactory mucosa and nasal tissues. Early infections results in necrosis (tissue death) and hemorrhaging in the olfactory bulbs. The amoeba then climbs along nerve fibers, through the floor of the cranium, into the brain. Naegleria infection can only result from exposure to the amoeba's environment, not from person-to-person contact.

*Signs and Symptoms of Naegleria Infection*

This parasite attacks the human nervous system, causing primary amoebic meningoencephalitis (abbreviated PAM or PAME). Initial symptoms of PAM begin 1 to 14 days after infection, and can include headache, fever, nausea, vomiting, and stiff neck. The progressive destruction of brain tissue leads to confusion, disorientation, loss of balance, seizures, and hallucinations. Once symptoms begin, the disease quickly progresses, typically resulting in death within one week.

*Where Is Naegleria Found?*

Naegleria fowleri has a worldwide distribution, inhabiting lake water and soil. It is a free living amoeba typically found in warm fresh water, at temperatures ranging from 77 95 degrees F. High risk habitats include:

* Warm bodies of freshwater
* Geothermal hot springs
* Warm water discharge from industrial plants

*How to Reduce Your Risk*

Infection usually follows water-related activities such as swimming underwater, diving, or any water sport that results in water going up the nose.You can reduce your risk of infection by:

* not swimming in warm freshwater, hot springs, and the thermally-polluted water around power plants.
* not swimming during heat waves, particularly when water volume is low.
* using nose clips when jumping or diving into bodies of warm freshwater.
* trying not to disturb the sediment while swimming in shallow, warm freshwater areas.

*Sources and Resources*

To find additional resources on PAME and the biology of infectious disease see the following websites:

* CDC's Naegleria Infection Fact Sheet
* CDC's Diseases & Condition A Z Index

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