As Americans find ways to cope with an unusually sweltering summer, many of them have taken to bodies of water to cool off. But at least two people who ventured to freshwater swimming holes this summer have died after contracting an amoeba that devours brain tissue.
A man died after he was infected by the amoeba, whose scientific name is Naegleria fowleri, the Georgia Department of Public Health said. Earlier this month, Nevada public health officials said a boy died of the same infection after he probably came into contact with the amoeba at Ash Springs, a hot springs about 100 miles north of Las Vegas.
Here's what to know about Naegleria fowleri, where it's found and how to recognize or avoid an infection.
What is the brain-eating amoeba Naegleria fowleri?
Naegleria fowleri is also known as the brain-eating amoeba because of the damage it can cause to the human brain.
An infection by the amoeba happens when it enters the body through the nose "during water-related activities" - such as splashing, swimming or submerging - and then travels to the brain, according to the Centers for Disease Control and Prevention. The brain infection is called primary amebic meningoencephalitis, which the CDC says is "usually fatal."
The amoeba is thermophilic, which means it enjoys warm environments, according to the CDC.
Where is the brain-eating amoeba found and is it common?
Naegleria fowleri is common in the environment but infections are extremely rare, said Emma H. Wilson, a professor of biomedical sciences at the University of California at Riverside. There are only about three cases per year in the United States.
The amoeba is found around the world in warm freshwater, such as lakes, rivers and hot springs. It is also found in soil. It cannot survive in saltwater and has never been detected in seawater, the CDC says.
The amoeba is also moderately sensitive to chlorine, at about the same range as giardia intestinalis - another pathogen that can be contracted through water but is usually far less fatal. The amoeba cannot survive in swimming pools that are properly chlorinated, but it has been found in rare instances in swimming pools that were not well maintained.
It cannot be contracted solely by swallowing contaminated water but can infect people when they use contaminated water to rinse their sinuses, the CDC says.
Most infections in the United States happen during summer and in the South, but in recent years, they have been detected farther north during bouts of extreme heat, according to the Cleveland Clinic and a 2021 study. The "change in where infections happen could be due to climate change," according to the clinic.
What are the symptoms of a brain-eating amoeba infection?
Signs of an infection "come on suddenly and are severe at the start," according to the Cleveland Clinic. The first symptoms, according to the CDC, usually start five days after the infection but can show up as late as 12 days after contact.
After symptoms start, the infection "progresses rapidly and usually causes death within about 5 days," the CDC says.
Symptoms to look out for include headache, fever, nausea and vomiting.
Later in the infection, symptoms can include "stiff neck, confusion, lack of attention to people and surroundings, seizures, hallucinations, and coma," according to the CDC. People with these symptoms should seek medical attention immediately, especially if they've recently been in warm bodies of freshwater.
What are the treatments for a brain-eating amoeba infection?
With infections being so rare, scientists have not come to conclusions about effective treatments. But there is some evidence that drugs such as miltefosine may be effective, according to the CDC, as it has been used to treat three previous survivors. Only four people are known to have survived an infection between 1962 and 2022.
Wilson said although the infection was considered not treatable for many years, it is now more quickly recognized. Treatment is now "quicker and more successful and there are some people that survive," she said.
People who suspect they have come in contact with Naegleria fowleri should not panic, Wilson said, because it "is unlikely that you have this." But if you experience a sudden and severe onset of headaches, fever and vomiting after possible exposure, see a doctor immediately, she said.
How can I avoid Naegleria fowleri?
The CDC advises people to assume that the amoeba is present in any warm body of freshwater in the United States, regardless of the region.
Although the relationship between the presence of the amoeba in the water and infection is unclear, the CDC advises that the best way to reduce the risk of an infection is to try to avoid getting water up the nose. If you're in an area where the amoeba could be present, avoid jumping in the water and "ideally keep your head above the water," Wilson said.
When using sinus-clearing devices such as a neti pot, make sure to use sterilized water, she added.
The amoeba also thrives in sediment at the bottom of bodies of water, so people should avoid stirring up the matter.