CBS News -- Two 12-year-olds are batting a rare "brain-eating amoeba" that has claimed the lives of 99 percent of the people it infects.
Both Kali Harding of Arkansas and Zachary Reyna from Florida developed primary amebic meningoencephalitis (PAM), an infection caused when an amoeba called Naegleria fowleri enters through the nose and attacks the brain.
Zachary's family said on their Facebook page Wednesday that the young boy is still battling the infection at the hospital.
"Again we love and thank you all so much. Zac is a fighter and will continue to fight. We are praying and believing for big changes in Zac and all of our lives," his family wrote.
The News-Press in Ft. Meyers, Fla. reported that Zac was taken to the hospital this past weekend with severe flu-like symptoms. His family members said later that doctors diagnosed him with the infection. The Florida Department of Health confirmed to CBSNews.com that a patient in the area had PAM, but did not identify the boy by name.
Kali, who contracted PAM in late July, is recovering, according to her family's Facebook page. She recently wrote "Kali Harding loves Daddy," and continues to have signs of further improvement.
The disease-causing microbe -- which is commonly found in warm, freshwater bodies up to 115 degrees F and soil -- can cause an infection that makes the brain tissue swell, known as meningitis.
Naegleria fowleri can only cause the infection if it swims up a person's nose, which is why lake swimmers and divers are more vulnerable. You cannot contract the infection if you drink contaminated water or if you are swimming in a properly cleaned, maintained and disinfected source of water. The microbe cannot survive in salt water.
The amoeba is most commonly found in the summer months in the southern United States, according to the Centers for Disease Control and Prevention.
PAM symptoms start around one to seven days after the amoeba enters the nose. People are observed having a headache, fever, nausea, vomiting, stiff neck, confusion, having problems paying attention to people and surroundings, problems with balance, seizures and hallucinations. The infection usually results in death five days after the onset of symptoms.
Although often fatal, the infection is extremely rare. Between 2003 and 2012, the CDC identified 31 cases of PAM infection. Twenty-eight were likely caused when the people swam in recreational water, and three cases may be rooted to patients who used contaminated water for nasal irrigation.
Kali likely contracted the amoeba when she visited Willow Springs Water Park in Little Rock, Ark., according to the CDC and the Arkansas Department of Health. The water park is located at a sand-bottomed lake, and the owners have said they voluntarily closed down the facility until they can find a way to put a solid bottom on the body of water to prevent further illness.
Florida Health Officials have not pinpointed a source of infection for their victim, citing the fact that since the amoeba is quite abundant in nature it could be hard to find out the root cause of the illness. However, family friends have said that Zachary was playing with two other children in a LaBelle residential canal. The two other children did not get the infection, however.
Other recent cases of PAM include a nine-year-old Minn. boy who had been swimming in a lake and 10 Pakistani victims who may have been using or bathing or swimming in contaminated water.
To prevent PAM when swimming in warm fresh waters, keep your head out of the water, use nose clips or hold the nose shut when entering the water. Avoid kicking up dirt and sediment in shallow, freshwater areas.
If you use nasal irrigation, make sure the water is disinfected. People can either boil it for one minute, use distilled or sterile water or filter the water with a device with an absolute pore size of 1 micron or smaller.