About Naegleria infection

Naegleria infection is caused by the amoeba Naegleria fowleri — a microscopic organism that lives in fresh water and soil. Naegleria infection most often occurs when the naegleria amoeba enters your body through your nose while swimming or participating in water sports. Once inside your nose, the amoeba makes its way to your brain. There, it causes inflammation and destroys brain tissue.

Naegleria infection is very rare. Only 31 cases occurred in the United States between 1989 and 2002. About 200 cases of naegleria infection have been reported worldwide.

Treatment with certain drugs may be successful if given early in a naegleria infection. But most naegleria infections result in death. Avoiding certain warm bodies of fresh water and wearing nose clips while in the water may help prevent such infections.


Naegleria infection causes a disease called primary amebic meningoencephalitis (muh-ning-go-uhn-sef-uh-LIE-tis), or PAM for short. This disease causes brain inflammation and destruction of brain tissue.

Early signs and symptoms of naegleria infection generally occur within one to two weeks of infection. Signs and symptoms may include:

  • A change in smell or taste
  • Fever up to 104 F (40 C)
  • 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 three to seven days.



Naegleria infection occurs when you are infected with an Naegleria fowleri amoeba.

Naegleria amoebas live in fresh waters

These amoebas are commonly found in warm bodies of fresh water. Examples include:

  • Lakes
  • Ponds
  • Hot springs
  • Warm water discharge from industrial plants
  • Pools that are improperly maintained or inadequately chlorinated

Infection enters through your nose
Naegleria infection occurs when water containing N. fowleri amoeba flows into your nose. The amoebas are also found in soil. It’s possible you could be infected by inhaling contaminated dust through your nose, as well.

After the amoeba enters your nose, it penetrates your nasal mucous membranes and makes its way to your brain through your olfactory nerve. Once in your brain, naegleria causes inflammation and usually fatal destruction of brain tissue.

Not everyone gets infected
Not everyone exposed to N. fowleri amoebas will become infected. Only one in every 2.6 million exposures to the amoeba leads to infection. Why some people become infected after exposure and others don’t isn’t known.

Naegleria infection is rare. You’re likely at some — although low — risk of naegleria infection anytime you swim or participate in water sports in freshwater lakes, rivers and hot springs. This is particularly true in higher risk areas such as the southern United States. You may also be at greater risk during warm and dry summer months. This is especially true during years when there are heat waves. Improperly chlorinated or poorly maintained swimming pools also may put you at risk.


Initial signs and symptoms of naegleria infection can resemble those of bacterial meningitis. Bacterial meningitis is a different type of infection and inflammation of your brain and spinal cord. This similarity can make it difficult to confirm a diagnosis of naegleria infection. Your doctor may do a number of tests, such as blood tests and imaging tests of your brain, to help rule out other possible causes.

Your doctor will likely perform a lumbar puncture to look for amoebas. During a lumbar puncture, or spinal tap, you typically lie on your side with your knees drawn up to your chest. Then a needle is inserted into your spinal canal — in your lower back — to collect cerebrospinal fluid (CSF) for testing. CSF is the fluid that protects your brain and spinal cord from injury. Your doctor may not find amoebas in the collected fluid, but this test may also help your doctor rule out other causes.


Most naegleria infections are difficult to treat successfully. But if caught early and treated aggressively, it may be possible to survive a naegleria infection.

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

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 bodies of fresh water such as lakes, rivers, hot springs and polluted water around power plants.
  • Don’t swim or jump into fresh water during periods of high temperatures and low water volume.
  • 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.
  • Don’t swim in posted “No swimming” areas or in areas where there are warnings of increased naegleria-infection risk.