Giardia

No, I don't have it. But someone I know posted a great quote:

"It's like your ass is a barista and mocha lattes are on backorder...I shit myself a couple times. I would have to bolt in the middle of meetings at work. When you burp it smells like sulfur."

Fortunately the danger of getting it is somewhat overstated, at least in the Sierra:

http://www.yosemite.org/naturenotes/Giardia.htm

Been there, done that.

Explosive diahrea and sulphurus farts.

Not fun.

Yeah, I went on this 26-mile backpacking trip this past weekend, and we came upon this "lake" at mile 16 where we were to camp for the night. So we bust out the filter, and gawd-damn the water looks like shit!! But..... so far, so good :D