Zachary Reyna, a seventh grader, was playing near a ditch Saturday and came home with what his mother thought was a 24-hour virus, WBBH-TV, Fort Myers, Fla., reported.
Within hours he underwent brain surgery at Miami Children's Hospital. He was diagnosed with primary amoebic meningoencephalitis, or PAM, caused by the amoeba Naeglaria Fowleri, or "brain-eating amoeba," found in still, warm water.
The amoeba enters the body through the nose and travels to the brain, destroying brain tissue, WBBH-TV said, noting only three people have ever survived the attack.
Zachary is in the hospital's intensive care unit.
The U.S. Centers for Disease Control and Prevention said 31 such infections were reported between 2002 and 2012.