There are no means yet known that would control naturally occurring Naegleria fowleri levels in lakes and rivers making prevention difficult. Because of this, swimmers and other recreational water users should assume that there is always a low level of risk whenever they enter warm freshwater lakes, rivers, and hot springs (for example, when swimming, diving, or waterskiing), particularly in southern-tier states.
What You Can Do
The only certain way to prevent a Naegleria fowleri infection due to swimming is to refrain from water-related activities in warm freshwater. Personal actions to reduce the risk of Naegleria fowleriinfection should focus on limiting the amount of water going up the nose.
These actions could include:
- 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 water-related activities in warm freshwater during periods of high water temperature.
- Avoid digging in, or stirring up, the sediment while taking part in water-related activities in shallow, warm freshwater areas.
These recommendations make common sense but are not based on any scientific testing since the low numbers of infections make it difficult to ever show that they are effective.
Routine, enhanced education of the public in advance of the summer swim season might be helpful. Education should put Naegleria fowleri infection in the context of other risks associated with recreational water use to help raise awareness and assist swimmers in making informed choices about their recreational activities. Healthcare professional education may be useful in speeding diagnosisand treatment.
Environmental Testing & Posting Signs
In general, CDC does not recommend testing untreated rivers and lakes for Naegleria fowleri because the ameba is naturally occurring and there is no established relationship between detection or concentration of Naegleria fowleri and risk of infection. Environmental testing may be warranted for investigations in which Naegleria fowleri detection may be useful for establishing geographical distribution in new environments 1, survival in disinfected water bodies, or in household water systems2.
Posting signs based on finding Naegleria fowleri in the water is unlikely to be an effective way to prevent infections. This is because:
- Naegleria fowleri occurrence is common, infections are rare.
- The relationship between finding Naegleria fowleri in the water and the occurrence of infections is unclear
- The location and number of amebae in the water can vary over time within the same lake or river3-7.
- There are no rapid, standardized testing methods to detect and quantitate Naegleria fowleri in water.
- Posting signs might create a misconception that bodies of water without signs or non-posted areas within a posted water body are Naegleria fowleri-free.