Which of the following is a risk factor for Naegleria fowleri infection?

Naegleria fowleri is a free-living amoeba commonly found in warm freshwater environments, such as lakes, hot springs, and poorly maintained swimming pools. The risk of infection increases significantly when individuals are exposed to warm freshwater, particularly in shallow areas where the water is more likely to be stagnant and warm. This amoeba enters the body through the nose, especially during activities such as swimming, diving, or other water exposure, leading to a rare but often fatal brain infection known as primary amoebic meningoencephalitis (PAM).

While exposure to saltwater and chlorinated pools can present different health risks, they are not associated with Naegleria fowleri infections. Saltwater environments typically do not support the growth of this amoeba, and chlorinated pools, when properly maintained, help to eliminate pathogens, including Naegleria fowleri. Drinking untreated water, although concerning for other pathogens and potential infections, is also not a recognized route for acquiring Naegleria fowleri; the primary risk relates directly to nasal exposure to contaminated freshwater.