The brain-eating amoeba Naegleria fowleri is moving further into the U.S., with a "statistically significant northward trend" observed since 2010, the U.S. Centers for Disease Control and Prevention (CDC) says. This shift may be the result of climate change, with warmer temperatures potentially facilitating its spread into areas that would have otherwise been unfavourable to the organism.
N. fowleri is a single-celled organism often found in warm freshwater systems such as lakes and rivers, as well as soil. It causes primary amebic meningoencephalitis—a central nervous system disease that leads to inflammation and destruction of the brain. Almost all cases are fatal, with just five known survivors across North America.
In recent months, there have been at least two fatalities due to the brain-eating amoeba N. Fowleri. Thirteen-year-old Tanner Lake Wall, from Florida, died a few days after being infected with the amoeba while swimming in a lake. Josiah McIntyre, 6, died a week after falling ill at his home in Texas last month.
The Texas Commission on Environmental Quality (TCEQ) is currently carrying out a major disinfectant program after N. fowleri was found in the water supply of the city of Lake Jackson. Initially, state officials issued a Do Not Use Water Advisory to eight cities, but the warning was later lifted for all but Lake Jackson. It is thought the entire decontamination process could take months.
"The City has concluded extensive flushing activities and is monitoring disinfectant levels to ensure chlorine is getting through the entire distribution system," a TCEQ spokesperson told Newsweek in an email. "Of greatest importance in managing Naegleria fowleri is maintaining a disinfectant residual throughout the entire drinking water distribution system." They said that once this level has been achieved, it will have to be maintained for at least 60 days.
Jennifer Cope, medical officer at the CDC's Waterborne Disease Prevention Branch, told Newsweek how or when N. fowleri got into the city's water supply is unknown. "The ameba is found naturally in water and soil and can gain entry into a municipal system when there is a disruption in the distribution system, such as when a pipe breaks," she said.
N. fowleri cannot infect a person through drinking water. Instead, the amoeba enters the brain when contaminated water goes up the nasal passage. Initial symptoms include severe headache, nausea and vomiting. As the disease progresses, people start suffering from a stiff neck, seizures and coma. The average sufferer dies around five days after infection.
While very rare, it is thought some cases are missed as symptoms are similar to bacterial meningitis. Three-quarters of cases are only diagnosed after death. While official records show there have never been more than eight deaths from N. fowleri per year in the U.S., a CDC report suggests the actual figure is closer to 16 per year. Most cases are in children and young men, as these groups are more likely to take part in watersports and activities where the risk of infection is higher.
"Each year, hundreds of millions of visits to swimming venues occur in the U.S. that result in just a handful of infections every year," Cope said. "Our data show that the numbers of cases have been stable over time with no detected increases."
However, she also said the geographic picture of N. fowleri is shifting north. While most cases are found in Texas and Florida, infections have also been recorded in Indiana, Maryland, Missouri, Kansas and New Mexico.
"Where Naegleria fowleri infections occur in the United States is 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."
Cope said N. fowleri is a "thermophilic organism," meaning it thrives in heat and likes warm water. This is why it tends to be found in regions where there is warm fresh water. "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," she said.
Dennis Kyle, a cellular biology professor at the University of Georgia, also said climate change could increase the risks of the brain-eating amoeba. In an interview with the Miami Herald last year, he said: "I don't think there's any doubt that with climate change and increasing temperatures we're going to have more cases and more exposure."
For now, in Lake Jackson, people have been advised not to let water go up their noses while washing or bathing. Children should not be left unsupervised with hoses and sprinklers, and slip-n-slide activities should be avoided. Bath and shower taps should be run for five minutes before use. If using water for sinus-rinsing reasons, it should be boiled and cooled or distilled.
"The Boil Water Notice for the City of Lake Jackson remains in effect," a TCEQ spokesperson said.