Mayo Clinic Health Library

Naegleria infection

Updated: 08-04-2012

Definition

Naegleria (nay-GLEER-e-uh) infection is a rare and usually fatal brain infection caused by an amoeba commonly found in freshwater lakes, rivers and hot springs. Exposure occurs during swimming or other water sports.

The amoeba — called Naegleria fowleri — travels up the nose to the brain, where it causes severe damage. Most people who have naegleria infection die within a week.

Millions of people are exposed to the amoeba that causes naegleria infection each year, but only a handful of them ever get sick from it. Health officials don't know why some people develop naegleria infection while others don't.

Avoiding warm bodies of fresh water and wearing nose clips while in the water may help prevent such infections.

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Symptoms

Naegleria infection causes a disease called primary amebic meningoencephalitis (muh-ning-go-un-sef-uh-LIE-tis). This disease causes brain inflammation and destruction of brain tissue.

Generally beginning within two to 15 days of exposure to the amoeba, signs and symptoms of naegleria infection may include:

  • A change in the sense of smell or taste
  • Fever
  • Sudden headache
  • Stiff neck
  • Sensitivity to light
  • Nausea and vomiting
  • Confusion
  • Loss of balance
  • Sleepiness
  • Seizures
  • Hallucinations

These signs and symptoms can progress rapidly. They typically lead to death within a week.

When to see a doctor
Seek immediate medical attention if you develop a sudden onset of fever, headache, stiff neck and vomiting.

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Causes

Naegleria infection is caused by the Naegleria fowleri amoeba, which is commonly found in warm bodies of fresh water around the world, usually during the summer months. The amoeba is also sometimes found in soil. The amoeba enters your body through your nose, via contaminated water or dust, and travels to your brain through the nerves that transmit your sense of smell.

Only a tiny percentage of the millions of people who are exposed to Naegleria fowleri ever get sick from it. Why some people become infected after exposure and others don't isn't known.

The amoeba isn't spread from person to person or by drinking contaminated water. And properly cleaned and disinfected swimming pools don't contain the naegleria amoeba.

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Risk factors

In the United States, millions of people are exposed to the amoeba that causes naegleria infection each year, but fewer than 10 people a year get sick from it.

Some factors that might increase your risk of naegleria infection include:

  • Freshwater swimming. Most people who become ill have been swimming in a freshwater lake within the past two weeks.
  • Heat waves. The amoeba thrives in warm or hot water.
  • Age. Children and young adults are the most likely age groups to be affected, possibly because they're likely to stay in the water longer and are more active in the water.
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Preparing for your appointment

If you believe you or your child may have naegleria infection, seek immediate medical attention. You might want to make a list of answers to the following questions to tell your doctor:

  • What are the signs and symptoms?
  • When did they start?
  • Does anything make them better or worse?
  • Has the person been swimming in freshwater within the past two weeks?
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Tests and diagnosis

Imaging tests
Computerized tomography (CT) or magnetic resonance imaging (MRI) can reveal swelling and bleeding within the brain.

  • CT scan. This procedure combines X-ray views taken from many different directions into detailed cross-sectional images of the brain.
  • MRI. An MRI machine uses radio waves and a strong magnetic field to produce extremely detailed images of soft tissues, such as the brain.

Spinal tap (lumbar puncture)
Naegleria amoeba can be seen under a microscope in the fluid that surrounds your brain and spinal cord. The spinal fluid is obtained by inserting a needle between two vertebrae in your lower back. This test also can measure the cerebral spinal fluid pressure and look for inflammatory cells.

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Treatments and drugs

Few people survive naegleria infection, even with treatment. Early diagnosis and treatment are crucial for survival.

The primary treatment for naegleria infection is an antifungal drug, amphotericin B — usually injected into a vein (intravenously) or into the space around your spinal cord to kill the amoebas.

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Prevention

The Centers for Disease Control and Prevention suggests that the following measures may reduce your risk of naegleria infection:

  • Don't swim or jump into warm freshwater lakes and rivers.
  • Hold your nose shut or use nose clips when jumping or diving into warm bodies of fresh water.
  • Avoid disturbing the sediment while swimming in shallow, warm fresh waters.
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