On Wednesday, the Southern Nevada Health District confirmed the death of a male under the age of 18 who may have been exposed to the amoebaduring a visit to the Lake Mead National Recreation Area.
N. fowleri is a single-celled organism that can cause a disease known as primary amebic meningoencephalitis (PAM), which results in severe brain damage and has a fatality rate of more than 97 percent, according to the U.S. Centers for Disease Control and Prevention (CDC).
The amoeba is found in warm freshwater bodies, such as lakes, rivers, ponds, canals, and even poorly-maintained heated pools.
“It probably lives in the silt at the bottom of these bodies of water,” Jimmy Whitworth, a professor from the London School of Hygiene & Tropical Medicine, told Newsweek. “It is never found in seawater or well-maintained swimming pools.”
Despite millions of exposures annually across the United States, N. fowleri infections are extremely rare.
“Very rarely it can cause an extremely nasty infection in humans, when it directly invades the brain through the nose, and digests brain cells,” Whitworth said.
The initial symptoms of PAM, which appear anywhere between one and 12 days after infection, include a stiff neck, confusion, lack of attention to the surrounding environment, loss of balance, seizures and hallucinations. After the appearance of symptoms, the disease progresses rapidly.
“It usually takes a few days—usually five—after exposure to manifest with symptoms such as headache, fever and altered mental state. It is almost always rapidly fatal,” Whitworth said.
In the period from 1962 to 2021, 154 cases of PAM were recorded in the United States, with just four of these individuals surviving the disease, CDC figures show.
Most infections have occurred in southern states, such as Florida and Texas. However, evidence suggests that the range of the amoeba is shifting northwards, possibly due to climate change, which is contributing to warmer water temperatures in freshwater bodies and lower water levels in some regions.
“Naegleria is only active in warm water, above 30 degrees Celsius [86 degrees Fahrenheit]. It may be expanding its range in response to climate change,” Whitworth said. “In the United States, where about three cases per year are diagnosed, it has been reported for the first time in recent years as far north as Nebraska and Minnesota.”
“In Europe, it has been reported in Italy and Spain, and further north associated with hot springs. It is probably underdiagnosed and unrecognized in other parts of the world, so the picture of whether it is truly expanding its range is not yet clear.”
Jennifer Cope, medical officer at the CDC’s Waterborne Disease Prevention Branch, previously told Newsweek the regions where infections occur in the United States are changing.
“In 2010, the first Naegleria infection was reported from Minnesota, 600 miles farther north than any previously reported case. We are seeing a statistically significant northward trend in the latitude of water exposures among U.S. recreational water-associated cases.
“Climate change can potentially be a factor as we know that Naegleria grow and live in warm freshwater environments, but we don’t know to what extent.”
The death of the boy in Nevada is the first confirmed fatality caused by N. fowleri that has been linked to a possible exposure in the Lake Mead National Recreation Area.
Lake Mead—the largest reservoir in the country in terms of water capacity—has shrunk to record lows this year amid the ongoing megadrought affecting large swathes of the western U.S.
While the risk to the public from Naegleria fowleri is low, the CDC recommends that people take the following precautions when entering warm freshwater:
Avoid jumping or diving into bodies of warm freshwater, especially during the summer. Hold your nose shut, use nose clips, or keep your head above water when in bodies of warm fresh water. Avoid putting your head underwater in hot springs and other untreated geothermal waters. Avoid digging in, or stirring up, the sediment in shallow warm fresh water.
