The rare amoeba, Naegleria fowleri, lives in warm bodies of water such as lakes, rivers and hot springs. It infects people by entering the body through the nose and traveling to the brain, at which point it causes primary amebic meningoencephalitis.
The patient in this case, a male under the age of 18, might have been exposed while on the Arizona side of Lake Mead. He started developing symptoms a week later, which usually include headache, fever and nausea, then eventually seizures and coma.
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While infections are exceedingly rare, they are almost always fatal. There have been at least 154 primary amebic meningoencephalitis infections in the United States since 1962, with only four survivors, according to the CDC. Patients usually die within five days of the onset of symptoms.
"My condolences go out to the family of this young man," Dr. Fermin Leguen, district health officer for SNHD, said in a statement. "While I want to reassure the public that this type of infection is an extremely rare occurrence, I know this brings no comfort to his family and friends at this time."
Naegleria fowleri is most active during the summer months of July, August and September, and is usually found in bodies of water that are above 80 degrees.
The CDC advises that swimmers can protect themselves by holding their nose shut or using nose clips in warm fresh water, and avoiding digging or stirring up sediment.
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