An anonymous reader writes: The Naegleria fowleri amoeba typically feeds on bacteria in water and soil. Human digestive systems have no problem killing it, but inhaling water that carries the amoeba gives it the opportunity to work its way into the brain after it sneaks through the nasal mucus. It happens rarely, but 97% of people whose brains start swelling because of this amoeba end up dying. Like most microorganisms, N. fowleri can be neutralized with concentrated chlorine. However, the systems we use to deliver tap water aren't so clean. Researchers found that N. fowleri can easily survive for 24 hours when it's mixed with the types of biofilm that tend to reside in water pipes. Increasing chlorine levels isn't a good option, since its reaction with these biofilms can generate carcinogens.