Not presuming to give advice, but as long as I have no real pain (cramps don't count), can hold down enough fluids to stay reasonably hydrated, and my temp is under 102, I'll skip the doctor.
In the case of a small child or an old, frail person, of course, I would be a lot more cautious! They don't tolerate dehydration well.
BTW, if you do get Norwalk-like virus, you can be sure that someone you came into contact with (or who handled your food or utensils) did not wash their hands after using the toilet. No mystery about it- it's a virus found in feces.
For fun, start keeping a mental tally of the folks who use any public restroom you happen to be in who just go straight out the door, without stopping at the sink. (Especially in restaurants, this is an instructive exercise). You will find that it is at least 50%- usually more. (Women may be a little better at this, but published studies really do not show this...)