A rare, brain-eating amoeba is spreading across the US

The infection has a fatality rate of over 97%.
Ayesha Gulzar
Brain eating amoeba Naegleria fowleri
Brain eating amoeba Naegleria fowleri

iStock/Dr_Microbe 

A rare, brain-eating amoeba is spreading across the U.S. While most infections previously occurred in the South, more recent infections have been identified further North. Climate change and warmer temperatures are increasing the amoeba's ability to survive in areas where it previously couldn't.

What is the brain-eating amoeba?

Naegleria fowleri, commonly known as a brain-eating amoeba, is a single-celled organism that usually thrives in warm freshwater, but it's also been found in public splash pads. People become infected when the microscopic organism gets into their nose and enters the brain via the olfactory nerve, which relays information about smells from the nose to the brain.

Once the amoeba reaches its destination, it starts destroying the brain tissue, causing an infection known as primary amebic meningoencephalitis (PAM). It destroys the brain tissue by releasing toxic molecules. The immune system tries to fight the infection by sending immune cells and fluid to the brain. The combination of the toxic molecules and the immune response causes brain swelling and death.

With a fatality rate of over 97%, the infection moves quickly after contraction. The initial symptoms include headache, fever, nausea, and vomiting, followed by a stiff neck, confusion, seizures, hallucinations, and coma.

Symptoms can start one to 12 days after exposure, and death usually occurs within about five days. There is no known effective treatment, and a diagnosis almost always comes too late.

Only four of the 154 cases reported between 1962 and 2021 in the U.S. survived the infection. Only about 430 cases have ever been documented globally.

The brain-eating amoeba is spreading further north

While infections from this fatal microorganism are extremely rare, cases do appear to be creeping further north in the U.S.

The pathogen was discovered for the first time in Iowa this summer after a resident swam in a lake the south of the state. Out of precaution, the Iowa Department of Public Health closed the lake's beach for about three weeks.

The second case occurred in August after a child went swimming in the Elkhorn River. The state had never reported a PAM infection before.

Another boy died after being exposed to the amoeba at Lake Mead in Nevada. An investigation by the Southern Nevada Health District determined the boy may have been exposed in early October and began developing symptoms about a week later.

Though most infections in the United States have been attributed to people swimming in warm lakes, one known outbreak in Arizona stemmed from the use of warm groundwater, with the amoeba growing in a well.

The amoeba loves the heat

Naegleria fowleri becomes more prevalent as temperatures rise in freshwater lakes and rivers. Warmer temperatures not only facilitate the survival and growth of pathogens but also drives people into the water more, which can increase the risk of infections.

Climate change-induced warming means that amoeba can now be present in areas of the country where it didn't use to be, like in the north and west. It's also extending the amoeba's life span past the summer months.

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