Brain-Eating Amoeba

What Is a Brain-Eating Amoeba?

There are several species of Naegleria but only the fowleri species causes PAM. It was first identified in Australia, but this amoeba is believed to have evolved here in the U.S. N. fowleri is microscopic: 8 micrometers to 15 micrometers in size, depending on its life stage and environment. By comparison, a hair is 40 to 50 micrometers wide. Like other amoebas, Naegleria reproduces by cell division. When conditions aren’t right, the amoebas become inactive cysts. When conditions are favorable, the cysts turn into trophozoites — the feeding form of the amoeba.

Where Are Brain-Eating Amoebas Found?

Naegleria loves very warm water. It can survive in water as hot as 115 F. These amoebas can be found in warm places around the globe. N. fowleri is found in:

Warm lakes, ponds, and rock pits

Mud puddles

Warm, slow-flowing rivers, especially those with low water levels

Untreated swimming pools and spas

Untreated well water or untreated municipal water

Hot springs and other geothermal water sources

Thermally polluted water, such as runoff from power plants


Soil, including indoor dust

Splash pads for children

Water parks

What Are the First Symptoms Someone Might Have?

Symptoms of PAM are not specific to this disease. At first, PAM may seem like viral meningitis. Symptoms include:



stiff neck

loss of appetite


altered mental state



How Do People Get Infected With Brain-Eating Amoeba?

The term “brain-eating amoeba” makes the amoeba sound like a tiny zombie stalking your skull. But brains are accidental food for them.

According to the CDC, N. fowleri normally eats bacteria. But when the amoeba gets into humans, it uses the brain as a food source. The nose is the pathway of the amoeba, so infection occurs most often from diving, water skiing, or performing water sports in which water is forced into the nose. But infections have occurred in people who dunked their heads in hot springs or who cleaned their nostrils with neti pots filled with untreated tap water. A person infected with N. fowleri cannot spread the infection to another person.

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