Cripto-sporidium (If it's spelled that way) happened to me. I wake up in the morning with a wetness around my butt. I assume it's sweat, feel down there, and end up smelling stuff. I get up and pull off the blankets to find a large brown spot in the sheets, as well as my clothes. I told my parents and they started cleaning up the mess (this was many years ago). So I'm lying on the couch and start feeling nauseated. I first assume it will go away, but it just intensifies to the point of me admitting I feel absolutely horrible. I end up vomiting violently twice on the carpet before anyone could fetch a bucket. I was extremely weak, and just slept most of the week or two I was ill, vomiting every day. I don't remember much of anything during that, but I remember when I could walk again, I had to poop in a bag for parasite tests.
That's the worst experience I ever had in life. It all happened after I came back from summer camp. They had a small lake filled with fish and bird feces. I stuck my hands in the water like I thought nothing of it. Then went to lunch without washing my hands.