Free-living Ameba

Infections with free-living ameba (single-celled living organism) are rare and can cause a wide range of symptoms in people. Specific amebae known to cause infections in people include: Naegleria fowleriBalamuthia mandrillaris, and Acanthamoeba spp.

Spotlight on Naegleria fowleri infections in the U.S.

The risk of Naegleria fowleri infection is very low. There have been 37 reported infections in the U.S. in the 10 years from 2006 to 2015, despite millions of recreational water exposures each year. By comparison, in the ten years from 2001 to 2010, there were more than 34,000 drowning deaths in the U.S.

In 2011, a death in a school-aged child from the central region of Virginia was reported. The cause of death was confirmed by the U.S. Centers for Disease Control and Prevention as a free-living ameba called Naegleria fowleri.  This type of ameba can cause a rare, but severe infection of the brain. Naegleria fowleri is commonly found in warm fresh water (for example, lakes, rivers, and hot springs) and in soil.

Humans become infected when water containing Naegleria fowleri enters the nose, usually while swimming. People do not get infected by drinking contaminated water. Very rarely, infections have been reported when people submerge their heads, cleanse their noses during religious practices, or irrigate their sinuses (nose) using contaminated tap or faucet water. Once the ameba enters the brain, it causes an often fatal infection called primary amebic meningoencephalitis (PAM). The ameba has never been shown to have spread from one person to another.

How can I reduce the risk of an amebic infection while recreating?

  • Hold your nose shut, use nose clips, or keep your head above water when taking part in water-related activities in bodies of warm freshwater.
  • Avoid putting your head under the water in hot springs and other untreated thermal waters.
  • Avoid digging in, or stirring up, the sediment while taking part in water-related activities in shallow, warm freshwater areas.
  • Keep swimming pools and spas properly disinfected before and during use. Please visit the Office of Environmental Health’s website for more information.
  • Clean small blow-up or plastic kiddie pools by emptying, scrubbing, and sanitizing them between each use.
Clinicians: For 24/7 diagnostic assistance, specimen collection guidance, shipping instructions, and treatment recommendations, please contact the CDC Emergency Operations Center at 770-488-7100. More detailed guidance is under Information for Public Health & Medical Professionals. CDC no longer provides miltefosine for treatment of free-living ameba infections. Miltefosine is now commercially available. Please visit impavido.comexternal icon for more information on obtaining miltefosine in the United States. If you have a patient with suspected free-living ameba infection, please contact the CDC Emergency Operations Center at 770-488-7100 to consult with a CDC expert regarding the use of this drug.

For more information about free-living ameba infections and recreational water safety, please see the following resources: