TAMPA, Fla. (WFLA) — The Centers for Disease Control and Prevention said it had no confirmed cases of a “brain-eating amoeba” in Florida after a teen’s family said it infected his brain while he was swimming at the beach, WBBH reported.

According to the family, Caleb Ziegelbauer was infected with Naegleria fowleri, commonly known as the “brain-eating amoeba,” while swimming in Port Charlotte on July 1.

Caleb’s family said he began experiencing headaches and hallucinations a few days later, and he was taken to the emergency room. On Tuesday evening, he remained at the hospital, fighting for his life.

Doctors told Caleb’s parents a brain-eating amoeba went through his nose and infected the brain. But his fluid samples were tested and sent to the CDC, and they found no traces of the infection.

“This year, in the United States, there has been one confirmed case of Naegleria fowleri, in a patient who resided in Missouri,” an agency representative told WBBH. “CDC’s free-living ameba laboratory performed testing on two samples of cerebrospinal fluid (CSF) from this patient [Caleb] and Naegleria fowleri was not detected in either sample.”

Caleb’s aunt, Katie Chet, told the news station the tests were “inconclusive.”

“They couldn’t find it, but they couldn’t say it was negative for sure. Based on history, symptoms and how he’s presented kind of over the last two weeks. His medical staff on Wednesday kind of said that they’re mostly sure this is what they’re dealing with,” Chet said.

According to the CDC, N. fowleri typically occurs when people go swimming or diving in warm freshwater places, like lakes and rivers, and grows best at higher temperatures up to 115°F .

The infection can travel up the nose to the brain and destroy brain tissue. Symptoms include fever, headaches, stiff neck, seizures and hallucinations, among others.

More than 97% of those infected with N. fowleri die, according to the CDC.