A microscopic organism that attacks the brain, and can be deadly. An amoeba called naegleria fowleri, has caused the deaths of at least six people this year.
"There are many risks that have to do with water. This is one of them," Dr. Anthony Fauci, of the National Institutes of Health.
All of the victims had been swimming in warm lakes or under chlorinated pools in Florida, Texas and Arizona. Among them, 22-year-old Colby Sawyer, of Lubbock, who was infected while wakeboarding at Lake LBJ in August.
"He was just full of life and that was what he loved to do," said Tammy Sawyer, Colby's mother.
Sawyer began complaining of a headache after returning from the lake. Within a week he fell into a coma and died.
"My biggest fear, as a mom, is my child's going to drown at a lake," said Sawyer. "You never think that they're gonna contract some deadly disease that's gonna kill them in a matter of days."
Experts say infection is extremely rare, on average just over two cases per year. They're not sure what caused the spike this year. But they do know how the amoeba enters a swimmer's body through the nose where it then attacks the brain.
"Particularly when they dive. That's the real risk," said Dr. Fauci. "Because when the water has to get up through the nose and that's how it ultimately enters your system is through the nose."
Even though infection by the amoeba is rare, experts say if you are planning to swim in a lake, there are some steps you should take to protect yourself, like using nose clips to keep water out, and avoiding areas of very warm water.