As 12-year-old Zachary Reyna from southwest Florida fights for his life after contracting Naegleria fowleri, an amoeba found in warm freshwater that destroys brain tissues, the Florida Department of Health has issued a warning for swimmers.

The amoeba is found in warm freshwater bodies such as lakes, rivers, ponds and canals, and the current high temperatures in Florida increase the threat of swimmers contracting it, the warning said, adding that July, August and September are peak seasons for the amoeba.

"Infections usually occur when it is hot for prolonged periods, causing higher water temperatures and lower water levels," Swannie Jett of the Department of Health in Seminole County, Fla. told the Orlando Sentinel.

Carina Blackmore, Interim State Epidemiologist, said in a press statement that swimmers should take precautionary methods such as avoiding water-related activities when it's hot and limiting the amount of water that goes up the nose.

“If you are partaking in recreational swimming activities during this time, please take necessary precautions and remind your family and friends to do the same," Blackmore said.

According to the Centers for Disease Control and Prevention, or CDC, Naegleria fowleri infections called primary amebic meningoencephalitis, or PAM, are rare -- only 28 cases were reported in the U.S. between 2003 and 2012 -- but most prove fatal. Only three people have so far survived after contracting the infection, and hopes are high that Reyna would become the fourth survivor.

Twelve-year-old Kali Harding of Arkansas, who was diagnosed with the condition last month, is now the third survivor and doctors at Arkansas Children's Hospital said her condition is stable, the Huffington Post reported.

According to the CDC's website, initial symptoms such as headache, fever, nausea, vomiting and a stiff neck, appear within the first seven days, and, "After the start of symptoms, the disease progresses rapidly and usually causes death within one to 12 days."

Reyna is currently at the Miami Children's Hospital, and based on a message post on the Pray4Number4 Facebook page, his condition seems to be getting worse.

“I can't express how much we appreciate all the love and support you all are giving. Your prayers for Zac are being heard. We are still in the storm and it seems to be getting worse,” a message by his parents read.