Residents in Louisiana's St. Bernard Parish had to deal with a nasty brain-eating amoeba in their water supply last summer—and now the amoeba has made a return appearance. Water in the parish right outside New Orleans has tested positive for Naegleria fowleri, and officials say the state's Department of Health and Hospitals has ordered a "chlorine burn" to purge the system of the possibly fatal pathogen, ABC News reports. Naegleria fowleri can cause a rare, potentially deadly brain infection when contaminated water enters a person's body (usually by water going up the nose, per the CDC) and travels up to the brain. A statement from the state's Department of Health and Hospitals says two of the seven sites it tested came back positive for the amoeba; NBC News notes one of the two positive samples was of untreated water; the other was from a sampling station hit by a car, which may have caused untreated groundwater to leak into the supply.
The 225-mile water system that serves the parish used to provide about 68,000 residents with water, but Hurricane Katrina whittled that number down to about 44,000—and because of that decreased population and an increase in ecofriendly water devices, less water is being treated in the same system, which could end up creating the ideal breeding ground for the amoeba, per ABC. "Use is good because it pushes new water through the system," a health department spokeswoman tells NBC. If fresh water isn't continually forced through the pipes, it can lose the chlorine that kills the amoeba and become contaminated. Despite elevated concern from this news, the health department says it's still safe to drink the water—consumers should just take special care not to get it up their noses. (A 12-year-old Florida boy died in 2013 after being infected with the amoeba.)