23 people have died with this infestation, all in Florida, Texas or Arizona. The bug likes warm places and is stirredup from the sediment and into the water by waders. It can also live in swimming pools. Now, here's where it gets really ghoulish.
It enters via a swimmers nose, migrates up the olfactory nerve (the one that tells you that your neoprene needs a bath...but I digress) and up into the brain where it feeds. Folks unfortunate enough to serve as a dormitory for these little guys complain of headache (well, dah), fever and other nonspecific symptoms. Neurological symptoms occur next, and death follows within days. There is no cure.
Prevention: plug up your nose. Incidences are rare, but the fatality is 100% for those who have gotten it.