A 12-year-old boy died from a brain-eating amoeba two weeks after a holiday weekend on a popular South Carolina lake.

The brain-eating amoeba enters the body when water is forced up the nose, like when someone jumps or dives in the water.

It causes an infection that swells the brain and destroys tissue. Fewer than 10 cases are reported each year in the U.S., but almost all are fatal.

Here are some things to know about the amoeba, its latest victim and other dangers on freshwater lakes:

What is the brain-eating amoeba?

The amoeba’s scientific name is Naegleria fowleri and it is most dangerous in water that stays for a while over 77 degrees Fahrenheit (25 degrees Celsius), including in lakes and rivers in the southern part of the U.S. and other places with hot, sometimes dry summers like Pakistan and Australia.

The amoeba enters the brain through the olfactory nerve in the nose. Once inside, it causes an infection called primary amebic meningoencephalitis.

Symptoms start as a fairly standard headache and nausea. By the time the pain becomes severe, it is almost always too late to save the infected person. Of the 167 cases reported in the U.S. between 1962 and 2024, only four people have survived, according to the U.S. Centers for Disease Control and Prevention. Most of the deaths happened within five days of getting sick, according to the CDC.

One infection in a body of water doesn’t increase the chances of another infection in the same body of water, the agency said. The amoeba cannot move from one person to another.

It was the first death from the amoeba in South Carolina since 2016, the CDC said.

What happened?

Jaysen Carr went swimming at Lake Murray about 15 miles (24 kilometers) west of Columbia over the July Fourth weekend.

He got sick several days later and died on July 18.

His father and mother had never heard of the amoeba before a doctor in tears told them what tests of his spinal fluid had found.

Clarence Carr said he was shocked to learn South Carolina, like most other U.S. states, has no law requiring public reporting of deaths or infections from the amoeba. The lake wasn’t closed and no water testing was performed.

“My son was a very smart individual. If he had one warning, he would have thought swimming in the lake was a bad idea,” Carr said.

The amoeba is fairly common and is most dangerous when the water is warm.

Researchers are trying to figure out why the infections are so rare. Some people have been found to have had antibodies, signalling they may have survived exposure. Others may die from brain swelling and other problems without the amoeba ever being detected.

“My son lost his life swimming. We assumed it was safe,” Carr said.

The amoeba can show up in hot springs, rivers and, on rare occasions, in tap water. That’s why doctors recommend using sterile water for cleaning nasal passages with a neti pot.

The only way to be completely safe is to not swim in lakes or rivers and, if you do, keep your head above water. Pinching your nose or using nose clips when diving or swimming can keep water out of your nose.

Other dangers lurking in lakes and rivers

There are other dangers in swimming in lakes and rivers instead of pools, where chemicals can kill off dangerous bacteria and other organisms.

A mouthful of water could contain E.coli bacteria. And while the bacteria normally live in the intestines of healthy people and animals, some strains can cause a range of conditions, including urinary tract infection, cystitis, intestinal infection and vomiting, with the worst cases leading to life-threatening blood poisoning, according to the Mayo Clinic.

Algae can also cause illnesses. Cyanobacteria—also referred to as blue-green algae—are plant-like organisms that live in water.

The algae can look like foam, scum, mats, or paint on the surface of the water and can grow underneath it.

The organisms can quickly grow out of control, or “bloom,” in warm weather, helped along by excessive nutrients in fertilizers and pet waste carried along by stormwater.

Some of the algae produce toxins that can cause symptoms including skin irritation, stomach cramps, vomiting, nausea, diarrhea, fever, sore throat, headache, muscle and joint pain, mouth blisters, seizures, and acute liver damage, according to the U.S. Centers for Disease Control and Prevention.

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