- Naegleria fowleri is found mainly in warm freshwater and soil, including lakes, rivers, ponds, hot springs, and some poorly disinfected water systems.
- Naegleria fowleri infections are extremely rare, with only a small number of cases reported each year in the United States.
- Infection can be treated with a combination of medicines, but it is difficult to cure and requires immediate medical treatment.
Naegleria fowleri is a rare but dangerous amoeba that can infect the brain after entering the body through the nose. This infection, called primary amebic meningoencephalitis, progresses quickly and is often fatal.
This parasite is usually found in warm freshwater, such as lakes, rivers, and poorly treated pools. Although it does not spread from person to person, even brief exposure to contaminated water can lead to infection.
Treatment for Naegleria fowleri is difficult and typically involves strong medications like amphotericin B given in the hospital. Because early treatment offers the best chance of survival, recognizing the symptoms and seeking medical care right away is essential.
Main symptoms
The most common symptoms of Naegleria fowleri infection, or “brain-eating amoeba,” include:
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Headache and stiff neck
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Nausea and/or vomiting
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Fever
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Confusion, drowsiness, or in severe cases, coma
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Eye pain or discomfort due to sensitivity to light
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Seizures
Naegleria fowleri infects the central nervous system and causes primary amebic meningoencephalitis. Symptoms usually begin 1 to 12 days after exposure and are similar to those of bacterial meningitis.
Also recommended: Meningitis Symptoms: Online Quiz, Early Signs & Diagnosis tuasaude.com/en/meningitis-symptomsOnce symptoms start, they tend to get worse quickly over just a few days, putting the person’s life at risk. That’s why seeking emergency care right away is essential if infection is suspected.
Frequently asked questions
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Naegleria fowleri is a free-living ameba that lives naturally in warm freshwater and soil. It can be found in warm lakes, rivers, ponds, hot springs, freshwater sediment, inadequately disinfected recreational water venues, and some tap-water or geothermal water systems.
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Naegleria fowleri infection is extremely rare. In the United States, 180 cases were diagnosed from 1937 through 2025, with 0 to 8 cases reported per year.
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Naegleria fowleri infection can be treated with a combination of medicines, but there is no treatment that is reliably successful. Early diagnosis and immediate treatment offer the best chance of survival, and only a small number of people have survived.
Confirming a diagnosis
Diagnosis of Naegleria fowleri infection is made by an infectious disease specialist based on symptoms, recent activities in possibly contaminated water, and tests such as a brain MRI or lumbar puncture.
A lumbar puncture allows a sample of cerebrospinal fluid to be collected and analyzed. In some cases, the amoeba can be seen under a microscope, confirming the diagnosis. Specific tests like PCR or those that detect proteins produced by the parasite may also be used, but they aren’t always available because the infection is so rare.
How it's transmitted
Infection occurs when water contaminated with Naegleria fowleri enters a person’s nose. The parasite can then travel through the nasal passages to the brain.
Naegleria fowleri is usually found in freshwater sources such as rivers, hot springs, or poorly maintained pools, but it does not appear to live in saltwater. Because of this, infections are more common in people who swim or dive in freshwater.
Treatment options
Treatment for Naegleria fowleri infection must be directed by an infectious disease specialist. Although there are no consistently effective treatments, amphotericin B is typically used in combination with other medications.
There are only a few studies on the treatment options for the “brain-eating amoeba” Naegleria fowleri. While some people have survived with medical treatment, in most cases the infection progresses rapidly and is fatal.
Preventing infection
Naegleria fowleri infection is very rare, but you can lower your risk by following these precautions:
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Avoid swimming in freshwater that may be contaminated
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When doing nasal irrigation, only use sterile saline or water that has been boiled and cooled
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Make sure pool water at home is properly treated
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Wear nose clips when swimming or diving
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Avoid diving in hot springs
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Don’t stir up or dig in the sediment at the bottom of warm freshwater sources such as springs, lakes, ponds, or rivers
This infection is not contagious and can’t be spread from person to person. Although it is serious, it can be prevented with the right precautions.
