Naegleri fowleri is an amoeba that can cause a serious central nervous system infection. The amoeba is found in warm and still fresh water bodies of water and enters a human body through the nose. Successful treatment has included miltefosine.
Naegleria fowleri is an amoeba that lives throughout the world in warm and shallow bodies of fresh water, such as lakes, rivers and hot springs. It also lives in soil. It’s considered a free-living organism because it doesn’t need a host to live.
People who become infected by this amoeba develop a condition called primary amoebic meningoencephalitis (PAM). PAM is a very serious infection of the central nervous system that’s almost always fatal.
Note: You might also see the words “ameba” instead of “amoeba” and “amebic” instead of “amoebic.” Amoeba is more common than ameba, but both words refer to an organism with one cell.
The most common way of being infected by this type of amoeba happens when infected water goes into your nose. From there, the amoeba goes to your brain. This usually happens when you’re swimming, diving or doing something like water skiing in infected water. In extremely rare cases, the infected water can be heated tap water or swimming pool water that isn’t chlorinated enough.
You can’t be infected by swallowing infected water.
Luckily, there are only a few cases each year in the U.S. (estimated to be between zero and eight). Most of the cases happen in the southern states, such as Florida and Texas, and involve young males.
In later years, though, some cases have happened in northern states during periods of very hot weather. This change in where infections happen could be due to climate change.
Studies are being done that call into question how rare infection with Naegleria fowleri really is. Some people have antibodies to the amoeba, indicating that they’ve been infected and survived. Some cases of deaths attributed to meningitis have been reclassified as deaths due to brain-eating amoeba (Naegleria fowleri).
Another question is, why some people aren’t infected with the amoeba even though they’re in the same place doing the same things as people who’ve been infected?
The signs and symptoms of primary amoebic meningoencephalitis (PAM) come on suddenly and are severe at the start, including:
The fatality rate is higher than 97% even with treatment.
The infection occurs when the amoeba known as Naegleria fowleri gets into your brain through your nasal cavity. It can enter your body if you inhale any infected water. Usually, the amoeba lives in freshwater bodies of water that are warm, including hot springs (geothermal water).
You can also be infected by inhaling infected dust.
There have been other cases of reported infection by brain-eating amoeba (Naegleria fowleri) due to people using tap water rather than distilled or sterilized water to rinse out their noses with devices like a neti pot.
It takes about two to 15 days after you’ve been exposed to the amoeba for symptoms to develop.
No. There haven’t been any cases found where the infection spread from person to person. There are studies underway to see if the infection can spread by tissue or organ donation.
If a healthcare provider thinks you might’ve been infected by brain-eating amoeba (Naegleria fowleri), they’ll recommend a spinal tap — also known as lumbar puncture — to see if the organism is in your cerebrospinal fluid (CSF).
Your provider may also recommend a brain biopsy. During this procedure, they’ll take a tissue sample and examine it under a microscope to check for the presence of the amoeba.
The treatment of choice for primary amoebic meningoencephalitis (PAM), or infection with brain-eating amoeba (Naegleria fowleri) is the antifungal amphotericin B. Some survivors in North America were treated with a combination of drugs that included amphotericin B, rifampin, fluconazole and a drug called miltefosine. Miltefosine is a drug approved for treating leishmaniasis, a parasitic disease that’s spread by sandflies.
The best results (in two children who recovered completely) came from early diagnosis and treatment with the recommended drugs, along with cooling the body to below-normal temperature to treat brain swelling.
Because the outlook for this condition is so dire, prevention can be important, even though the condition is very rare. These are key things to remember:
The outlook for someone who is infected with Naegleria fowleri is very poor. Even with treatment, most people die from this condition. Coma followed by death usually happens in a week or 10 days after symptoms and signs begin.
If you get feverish or have a headache after you’ve been active in a warm freshwater body of water or after you’ve used tap water to irrigate your nasal pages, see a healthcare provider or go to the emergency room immediately. Early diagnosis and treatment of infection with brain-eating amoeba (Naegleria fowleri) is critical.
A note from Cleveland Clinic
Hearing about a condition caused by a brain-eating amoeba and knowing how dangerous it can be is certainly scary. If you think you may have been exposed to the amoeba, get immediate medical help. But it’s important to remember how very rare this condition is. You can do your part in preventing it by using only distilled or sterilized water to rinse your nasal passages and by avoiding water you suspect may be infected, especially in hot weather.
Last reviewed by a Cleveland Clinic medical professional on 11/29/2022.
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