Warmer temperatures extend risk of waterborne pathogens and algal blooms in North Carolina
Health officials say rising water temperatures in North Carolina are lengthening the season for harmful algae, Naegleria amoebas and Vibrio bacteria, though most tested recreational sites still meet safety standards.
A teenager in central North Carolina died last week from a rare infection caused by the Naegleria fowleri amoeba, and two other deaths this year have been linked to Vibrio vulnificus bacteria, prompting renewed public concern about water safety. Health officials attribute the incidents to unusually warm and low-flow water conditions that have persisted longer into the fall.
Meteorologist Shel Winkley of Climate Central explained that prolonged heat especially affects shallow or slow-moving waterways, allowing water to remain warm for extended periods. Data show that days reaching about 85 °F now typically continue until mid-October, compared with early October in the 1970s, giving algae and microorganisms a longer window to develop.
The North Carolina Department of Environmental Quality recently warned residents to avoid discolored or scummy water that may signal toxic cyanobacterial blooms. While heavy rainfall can carry nutrients into rivers and lakes, subsequent hot, dry weather creates the stagnant conditions that favor bloom formation.
Testing by Sound Rivers of more than 50 recreational sites in the Neuse and Tar-Pamlico watersheds found that most locations met state water-quality standards ahead of Labor Day, though a site at the Neuse Golf Club in Clayton recorded elevated bacteria levels.
"I feel like every time I swim in a lake, I hear about the brain-eating amoeba, but I'm willing to take that risk. It is very rare," said Andrea Torrico, who swam at Raleigh Beach over the holiday.
The infections remain uncommon, with fewer than ten Naegleria cases reported nationwide each year. Transmission typically occurs when contaminated water enters the nose, while Vibrio infections usually result from exposure of open wounds to seawater.
Raleigh Water Assistant Director Ed Buchan noted that the city’s treatment system uses ozone to break down algae-derived compounds that can affect taste and odor, and that the large volume of Falls Lake makes the municipal supply less vulnerable to heat-related issues.
State health officials continue to advise the public to avoid water that appears bright green, blue, discolored or scummy, to keep children and pets away from suspected algal blooms, and to keep water out of the nose when swimming in warm freshwater.