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Brain-Eating Amoeba Hospitalizes Man Who Swam In Lake Of Three Fires

Naegleria fowleri is a seriously nasty pathogen.


Rachael Funnell


Rachael Funnell

Digital Content Producer

Rachael is a writer and digital content producer at IFLScience with a Zoology degree from the University of Southampton, UK, and a nose for novelty animal stories.

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naegleria fowleri brain-eating amoeba
The amoeba can enter the brain through the nose. Image credit: Kateryna Con /

Primary amoebic meningoencephalitis (PAM) is the diagnosis given to patients infected with the “brain-eating amoeba” Naegleria fowleri. The deadly pathogen can enter the brain via a thin bit of bone at the base of our nasal cavity and, once inside, they have a devastating effect on the organ.

The beach at Lake of Three Fires in Iowa, Missouri, has closed due to one such case as a man who went swimming here later fell ill with PAM. The Iowa Department of Public Health (IDPH) announced that it’s been confirmed as an infection with N. fowleri, and while it hasn’t been definitively linked to the lake, freshwater swimming is a risk factor for the illness.


N. fowleri is a microscopic single-celled amoeba that’s found in warm freshwater which can include lakes, rivers, ponds, and any stored, untreated water. Infection rates are very rare, with the IDPH reporting only 154 known cases in the United States since 1962.

While rare, the disease comes with grim statistics.

“The fatality rate is over 97%," reports the Centers for Disease Control and Prevention (CDC). "Only four people out of 154 known infected individuals in the United States from 1962 to 2021 have survived."

How N. fowleri enters the brain may in part explain the rarity of PAM as the contaminated water needs to reach all the way to the base of the nose which is why it's strongly recommended that nobody uses untreated freshwater for nasal lavage. Here, the amoeba can travel along nerves into the brain where they can form cysts and cause debilitating and ultimately fatal symptoms if left untreated.


Symptoms of PAM include:
 - Severe headaches
 - Nausea and vomiting
 - Neurological complications such as paralysis

The disease develops rapidly and can be deadly in as little as 10 days. Unfortunately, its presentation mirrors other illnesses such as meningitis and its rarity means that reaching a diagnosis can be delayed to catastrophic effect.

Missouri officials have shared that the local resident is being treated in intensive care. Testing will now begin in the area as the IDPH and CDC try to ascertain if N. fowleri is indeed present in the Lake of Three Fires.

"It’s strongly believed by public health experts that the lake is a likely source, but we are not limiting the investigation to that source because it hasn’t been confirmed,” said the Missouri Public Health Department on Twitter. “Additional public water sources in Missouri are being tested.”

[H/T: NPR]


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