Overview

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.

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, severe 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, particularly if you have recently been in warm, fresh water.

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.

Risk factors

In the United States, millions of people are exposed to the amoeba that causes naegleria infection each year, but few people get sick from it. From 2005 to 2014, 35 infections were reported.

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 previous 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.

Prevention

The CDC suggests that the following measures may reduce your risk of naegleria infection:

  • Don't swim in 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.
July 16, 2015
References
  1. Naegleria fowleri — Primary Amebic Meningoencephalitis (PAM) — Amebic Encephalitis. Centers for Disease Control and Prevention. http://www.cdc.gov/parasites/naegleria/index.html. Accessed June 4, 2015.
  2. Seas C, et al. Free-living amebas. http://www.uptodate.com/home. Accessed June 4, 2015.
  3. Naegleria fowleri — General information. http://www.cdc.gov/parasites/naegleria/general.html. Accessed June 4, 2015.
  4. Naegleria fowleri — Treatment. http://www.cdc.gov/parasites/naegleria/treatment.html. Accessed June 9, 2015.
  5. Steckelberg JM (expert opinion). Mayo Clinic, Rochester, Minn. June 9, 2015.