In the summer of 2016, a 16-year-old boy was reported as the fourth U.S. PAM survivor. This patient was diagnosed within hours of presentation to the hospital and was treated with the same protocol used for the 12-year-old 2013 survivor. This patient also made a full neurologic recovery and returned to school.
Illness and Symptoms
You cannot get infected from drinking water contaminated with Naegleria. You can only be infected when contaminated water goes up into your nose.
Primary amebic meningoencephalitis (PAM) is a disease of the central nervous system. PAM is caused by Naegleria fowleri, a free-living ameba. It is a rare disease* that is almost always fatal; only 4 out of 154 people in the United States have survived infection from 1962 to 2021.
Signs and symptoms of Naegleria fowleri infection are similar to bacterial meningitis, which lowers the chances of diagnosing PAM at first.
People become infected when water containing Naegleria fowleri enters the nose and the ameba migrates to the brain along the olfactory nerve. People do not become infected from drinking contaminated water. Symptoms start 1 to 12 days (median 5 days) after swimming or having another nasal exposure to water containing Naegleria. People die 1 to 18 days (median 5 days) after symptoms begin. PAM is difficult to detect because the disease progresses rapidly so that diagnosis sometimes occurs after the patient dies. Signs and symptoms of the infection include:
- Severe frontal headache
- Fever
- Nausea
- Vomiting
- Stiff neck
- Seizures
- Altered mental status
- Hallucinations
- Coma
The disease is generally fatal; among well-documented cases, there are only five known survivors in North America: one from the United States in 1978, one from Mexico in 2003, two from the United States in 2013, and one from the United States in 2016. The first U.S. survivor’s condition gradually improved during a one-month hospitalization. The only reported side effect to treatment was a reduction in leg sensation for two months after discharge, which gradually improved. There was also no detection of Naegleria fowleri 3 days post-treatment. It has been suggested that the first survivor’s strain of Naegleria fowleri may have been less virulent, which contributed to the patient’s recovery. In laboratory experiments, a California survivor’s strain did not cause damage to cells as quickly as other strains, suggesting that it is less virulent than strains recovered from other fatal cases.
The Mexico survivor’s condition did not begin to improve until 40 hours after hospital admission. On day 22 of admission, there was no abnormality shown in the brain scan and the patient was discharged the next day. The patient was followed up for the next 12 months without any recurrence of disease.
After 35 years without a Naegleria survivor in the United States, during the summer of 2013, two children with Naegleria fowleri infection survived. The first, a 12-year-old girl, was diagnosed with PAM approximately 30 hours after becoming ill and was started on the recommended treatment within 36 hours. She also received the investigational drug miltefosine, and her brain swelling was aggressively managed with treatments that included therapeutic hypothermia (cooling the body below normal body temperature). This patient made a full neurologic recovery and returned to school. Her recovery has been attributed to early diagnosis and treatment and novel therapeutics including miltefosine and hypothermia.
The second, an 8-year-old child, is also considered a PAM survivor, although he has suffered what is likely permanent brain damage. He was also treated with miltefosine but was diagnosed and treated several days after his symptoms began. Therapeutic hypothermia was not used in this case.
In the summer of 2016, a 16-year-old boy was reported as the fourth U.S. PAM survivor. This patient was diagnosed within hours of presentation to the hospital and was treated with the same protocol used for the 12-year-old 2013 survivor. This patient also made a full neurologic recovery and returned to school.
Overall, the outlook for people who get this disease is poor, although early diagnosis and new treatments might increase the chances for survival.
References
- Marciano-Cabral F, Cabral G. The immune response to Naegleria fowleri amebae and pathogenesis of infection. FEMS Immunol Med Microbiol. 2007;51:243-59.
- Visvesvara GS. Free-living amebae as opportunistic agents of human disease. J Neuroparasitol. 2010;1.
- Yoder JS, Eddy BA, Visvesvara GS, Capewell L, Beach MJ. The epidemiology of primary amoebic meningoencephalitis in the USA, 1962-2008. Epidemiol Infect. 2010;138:968-75.
- Capewell LG, Harris AM, Yoder JS, Cope JR, Eddy BA, Roy SL, Visvesvara GS, Fox LM, Beach MJ. Diagnosis, clinical course, and treatment of primary amoebic meningoencephalitis in the United States, 1937–2013. J Pediatric Infect Dis Soc. 2014;Epub: 1–8.
- Seidel J, Harmatz P, Visvesvara GS, Cohen A, Edwards J, Turner J. Successful treatment of primary amebic meningoencephalitis. New Engl J Med. 1982;306:346-8.
- Vargas-Zepeda J, Gomez-Alcala AV, Vasquez-Morales JA, Licea-Amaya L, De Jonckheere JF, Lores-Villa F. Successful treatment of Naegleria PAM using IV amphotericin B, fluconazole, and rifampin. Arch Med Res. 2005;36:83-6.
- Linam WM, Ahmed M, Cope JR, Chu C, Visvesvara GS, da Silva AJ, Qvarnstrom Y, Green J. Successful treatment of an adolescent with Naegleria fowleri primary amebic meningoencephalitis. Pediatrics. 2015;135:e744-748.
- Cope JR, Conrad DA, Cohen N, Cotilla M, DaSilva A, Jackson J, Visvesvara GS. Use of the novel therapeutic agent miltefosine for the treatment of primary amebic meningoencephalitis: report of 1 fatal and 1 surviving case. Clin Infect Dis. 2016;62(6):774-6.
- John DT, John RA. Cytopathogenicity of Naegleria fowleri in mammalian cell cultures. Parasitol Res. 1989;76:20-5.
*Rare Disease
There is no universal definition of a “rare disease” but the U.S. Rare Disease Act of 2002 defined a rare disease as affecting less than 200,000 people in the U.S. and this definition has been adopted by the National Institutes of Health, Genetic and Rare Diseases Information Centers.
Brain-Eating Amoeba
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.
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Overview
What is brain-eating amoeba (Naegleria fowleri)?
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.
How do you get infected by brain-eating amoeba (Naegleria fowleri)?
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.
How common is an infection due to brain-eating amoeba (Naegleria fowleri)?
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?
Symptoms and Causes
What are the symptoms of infection with brain-eating amoeba (Naegleria fowleri)?
The signs and symptoms of primary amoebic meningoencephalitis (PAM) come on suddenly and are severe at the start, including:
- High fever.
- Very painful headache.
- Nausea and vomiting.
- Trembling.
- Symptoms like those of meningitis, including a stiff neck and extreme sensitivity to light (photophobia).
- Mental confusion.
- Coma.
The fatality rate is higher than 97% even with treatment.
What causes infection with brain-eating amoeba (Naegleria fowleri)?
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.
How long is the incubation period for infection with brain-eating amoeba (Naegleria fowleri)?
It takes about two to 15 days after you’ve been exposed to the amoeba for symptoms to develop.
Can I get infected with brain-eating amoeba (Naegleria fowleri) from being around someone who has it?
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.
Diagnosis and Tests
How is infection with brain-eating amoeba diagnosed?
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.
Management and Treatment
How is infection with brain-eating amoeba (Naegleria fowleri) treated?
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.
Prevention
How can I prevent myself from being infected with brain-eating amoeba (Naegleria fowleri)?
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:
- Don’t swim, wade or do watersports in warm freshwater locations, especially still waters, without nose plugs. Don’t go into the water at all if Naegleria fowleri is known to be present or likely to be present.
- Don’t use tap water for a neti pot or any other device that cleans your nasal passages. Only use distilled or sterilized water. If you must use tap water, make sure that you boil it for one minute and then let it cool. If you live somewhere that’s 6,500 feet above sea level, boil the water for three minutes and let cool.
- You can use filters to remove germs from water. Use filters labeled “NSF 53,” “NSF 58” or “absolute pore size of 1 micron or smaller.”
- You can also use chlorine bleach liquid or tablets to disinfect your water for cleaning your nose and sinuses. Disinfecting water for nasal use requires a different amount of bleach than disinfecting water for drinking.
- If you do develop symptoms of fever or headache after going into warm freshwater, tell your healthcare provider where you’ve been.
Outlook / Prognosis
What is the prognosis (outlook) for people who are infected with brain-eating amoeba (Naegleria fowleri)?
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.
Living With
When should I see my healthcare provider if I have questions about infection with brain-eating amoeba (Naegleria fowleri)?
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.
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