The Killer in the Lake - S5.E4

A contractor gets hit in the head with a tool, and later starts getting a pounding headache, dizziness, spotty vision, and nausea from having a nail punctured into his brain; a football player in college gets extreme headaches, a stuffy nose, and blurred vision from Aspergillus fungi entering his brain; in 2012, an 8-year-old boy suffers constant vomiting, fatigue, seizures, and eventually dies from amoebic meningitis after being infected with Naegleria fowleri.