Once on the Green River in Utah, when I hiked way down below the take out for the upper section and forgot my water bottle. It tasted good until I sucked in a mayfly that was stuck in the film. I didnt get sick.
Once on a little creek in Southern Utah.
I didnt get sick.
Once on a hike on the Appalachian trail.
I got sick this time. I dont know what it was but luckily it didnt hit me until about three hours after I got home. Three days later I could get finally get more than 10 feet from the toilet.
My grandparents used to get their drinking water from a spring at their summer cabin in Canada. I used to drink that all the time too and never got sick.
Patrick