The child, from Clark County, likely contracted the parasite from swimming in Lake Mead, one of the US largest reservoirs, located in both Nevada and Arizona, said public health officials.
The child may have encountered the parasite during a swim on the Arizona side of the lake earlier this month, with symptoms showing up about a week later, according to the Southern Nevada Health District.
“This is the first confirmed fatality caused by Naegleria Fowleri exposure at Lake Mead National Recreation Area,” the National Park Service said in a statement reported by CNN.
The parasite can be found in warm freshwater, and infection, while very rare, nearly always leads to death.
Recent scientific research has found evidence that the climate crisis is causing Naegleria fowleri to spread further north as water temperatures get warmer.
“My condolences go out to the family of this young man,” Fermin Leguen, a doctor with the Southern Nevada Health District, said in a statement.
“While I want to reassure the public that this type of infection is an extremely rare occurrence, I know this brings no comfort to his family and friends at this time.”
Naegleria fowleri, a single-celled organism, infects people by entering their noses and travelling to the brain, where it destroys brain tissue, according to the US Center for Disease Control (CDC).
It cannot be spread from drinking water, or from person to person, the agency adds. Symptoms often resemble a brain infection and can include headache, fever, nausea, stiff neck and seizures.
While the parasite lives across much of the world, infection is very uncommon. Between 2012 and 2021, only 31 cases were reported in the United States, the CDC reported. The death rate for the disease is around 97 per cent.
The parasite has been found before in warm-water springs around Lake Mead, according to the US National Parks Service.
One recent study found that between 1978 and 2018, instances of Naegleria fowleri infection in the US have been moving steadily northward. Most cases are contracted in southern and warmer states like Florida and Texas – but since 2010, it has been identified as far north as Minnesota and Indiana, the study notes.
One potential reason for this northward shift is the climate crisis, the CDC noted.
“As air temperatures rise, water temperatures in lakes and ponds also rise and water levels may be lower,” the agency says. “These conditions provide a more favorable environment for the ameba to grow.”
Lake Mead has been at the epicentre of the massive drought in the western US powered by the climate crisis. Lake levels this year dropped to record lows, and the region surrounding the lake is under “severe” drought conditions.