This summer, two people sadly died after being infected by Naegleria fowleri, an organism that is commonly referred to as a brain-eating amoeba. The first death occurred after a Missouri resident swam in a lake in southern Iowa; the second occurred after a child went swimming in an eastern Nebraska river.
Naegleria fowleri is a single-cell organism that can cause infection while a person is swimming in freshwater—in a lake, river, or hot springs, for example—by traveling up the nose and to the brain, per the Centers for Disease Control and Prevention (CDC). This rare infection is called primary amebic meningoencephalitis (PAM) and is usually fatal because it can lead to inflammation of the central nervous system, per the CDC. Because the infection is uncommon and hard to detect, most diagnoses are made after the infected person has died.
Naegleria fowleri lives in soil as well as freshwater, and it favors warm temperatures. In fact, warmer temps caused by climate change could allow Naegleria fowleri to move into territories previously considered too cold for it—including the Midwest region of the US—according to a 2021 study from the CDC.
The term brain-eating amoeba—coupled with the illness it can cause—sounds scary, especially because it makes headlines every summer. But before you rethink any weekend trips to local lakes or rivers, it’s important to remember just how rare these infections are. From 2012 to 2021, only 31 Naegleria fowleri cases have been reported in the US, per the CDC. Three of those didn’t occur after a person went swimming: Two occurred after people used contaminated tap water in a nasal rinse, and one occurred after a person came in contact with infected tap water on a backyard slip n’ slide. (To put the overall number into context: Lightning kills about 20 people each year in the US, per the National Weather Service.)
“The low number of infections makes it difficult to know why so few people have been infected compared to the millions of others who used the same or similar waters across the US during the same time period,” the Iowa Department of Natural Resources noted in a statement following the first reported death earlier this summer.
Of course, it can’t hurt to familiarize yourself with the signs of a Naegleria fowleri infection. Per the CDC, symptoms can begin anywhere from one to nine days after exposure, and the illness typically progresses in two stages. During the first stage, an infected person may experience fever, nausea, vomiting, and a severe frontal headache; during the second, they might experience seizures, stiff neck, altered mental status, hallucinations, and coma. If caught in time, PAM can be treated with a combination of drugs, including antifungals and antibiotics, per the CDC.
If you’re still worried about this, the CDC also recommends taking some common-sense measures when swimming in natural areas:
- Don’t dive or jump into bodies of warm freshwater, especially during summer.
- Keep your head above water, hold your nose shut, or use nose clips when in a body of warm freshwater.
- Don’t put your head under water in hot springs.
- Do not disturb the sediment in shallow areas of bodies of warm freshwater.
Again, the risk of dealing with a brain-eating amoeba is super low—but being aware and staying as safe as possible while swimming can help you enjoy the rest of summer without too much worry.