(CNN) A weekend swim left a young girl fighting for her life when she contracted a brain-eating amoeba with a 97% fatality rate.

Lily Mae Avant, 10, swam in the Brazos River and Lake Whitney in Bosque County near Waco over Labor Day weekend, according to CNN affiliate KWTX-TV

Then, on September 8, Lily "began having a headache, and it was quickly followed by a fever," according to a Facebook page created to support the girl . Her family thought it was a viral infection at first, but after visits to the family doctor and Lily having trouble sleeping, the family knew something was wrong.

"She was incoherent, unresponsive and was quickly swept up and taken to the ER," the family wrote on Lily's Facebook page.

Lily was then flown to Cook Children's Health Care System in Fort Worth where a spinal tap found she had contracted Naegleria fowleri

"It's every parent's worst nightmare," the girl's aunt, Crystal Warren, told KWTX Friday. "For this to happen to her when there were so many other people in the same waters on the same days we just don't understand why it was her."

Chris Dowdy, principal at Valley Mills Elementary School, confirmed to CNN that a 5th-grade student was "putting up a fierce battle for her life, caused by this awful amoeba."

"She is an outstanding student, but more importantly, she is just a tremendous person," Dowdy said. "Everyone in our community, state, and even the entire country is praying for this sweet child."

The Centers for Disease Control and Prevention says the amoeba is a single-cell living organism commonly found in warm freshwater like lakes and rivers. The amoeba enters the body through the nose, travels to the brain and destroys brain tissue, according to the CDC.

Between 2009 and 2018, the CDC says only 34 cases of the Naegleria fowleri infection were reported in the US. Only four people out of the 145 known cases survived between 1962 and 2018.

Warren told KWTX she's hopeful her niece "will be number five to survive."