How sick have you been and still been able to work?

I work pretty hard. I worked the day after spraining my knee. Could barely walk. Got heat exhaustion last summer. Went inside for an hour, drank some water, then went back at it for 6 more hours until 11:00 PM. But the runs? If I have the runs, I'm stationed very near a toilet. I'm not about to shit myself at a client's house. I learned that lesson the hard way a long, long time ago.