I do not know of a specific cryptosporidium outbreak in Ohio, but it does pop up on occasion. Often, it is a problem in daycare centers, since one child can easily spread it to every other child. I heard about one outbreak where the water used to water the lawns in a public park had been contaminated by an infected child running through the sprinkler. They would capture the run-off water, disinfect it, and sprinkle it on the lawns again, but the disinfection process had broken down, so the bug contaminated the entire tank of reclaimed water.
Ohio has had a few outbreaks of nasty things in the last year or so. Right now, mumps and measles are a problem.
What I am thinking of was related to some algae toxin. Usual methods of purification such as boiling wouldn’t work.