A 12-year-old girl is in critical condition at Arkansas Children's Hospital after contracting a deadly brain-eating parasite.

Kali Hardig has been diagnosed with primary amoebic meningoencephalitis - a rare form of meningitis caused by the amoeba Naegleria fowleri. She's thought to have contracted the infection from a sandy-bottom lake at Willow Springs Water Park in Little Rock, Ark., according to the Arkansas Department of Health.

The 85-year-old water park, which was linked to an earlier Naegleria infection in 2010, is now closed.

"Though the odds of contracting Naegleria are extremely low, they are just not good enough to allow our friends or family to swim," park owners David and Lou Ann Ratliff said in a statement.

Warm Weather Stirs Up Amoeba Warning

Naegleria thrives in warm, standing freshwater and the sediment of rivers and lakes. And while it's usually harmless, it can cause fatal brain swelling if inhaled through the nose.

"If concerned about Naegleria, avoid swimming, diving or other activities that push water up the nose, especially in natural waters when temperatures are high and water levels are low," Dr. Dirk Haselow of the Arkansas Department of Health said in a statement.

While exceedingly rare, Naegleria fowleri infections are almost always fatal. Only one person out of 128 infected in the United States between 1962 and 2012 has survived, according to the U.S. Centers for Disease Control and Prevention.

"After the start of symptoms, the disease progresses rapidly and usually causes death within about five days," the agency's website reads.

Brain-Eating Amoeba Eyed in Death of Minnesota Child

Early symptoms include a severe frontal headache, fever, nausea and vomiting, according to the CDC. But those can swiftly give way to a stiff neck, seizures, confusion and hallucinations as the amoeba makes its way up through the nasal cavity into the brain.

"People should seek medical care immediately whenever they develop a sudden onset of fever, headache, stiff neck, and vomiting, particularly if they have been in warm freshwater recently," according to the CDC.

Naegleria was eyed in the death of a Minnesota child last summer, when the state experienced a heat wave. And in the summer of 2011, the amoeba killed four people in Virginia, Florida, Kansas and Louisiana, all of whom had been swimming in freshwater lakes.

Willow Springs Water Park closed after a swimmer contracted Naegleria fowleri. (Image credit: Willow Springs Water Park/Facebook)