I have had countless stomach viruses over the course of my life. I've known they were stomach viruses because everyone around me also has them. The symptoms have always been diarrhea, stomach cramps, temperature, feeling like utter shit, nausea but no vomiting.
My DH, my father, my BIL and my FIL are the same (we've gone down with it as a family before.)
I heard it's something to do with being a secretor or a non secretor (don't ask me what that is) but if you are a non secretor, you are apparently more likely to have blood type B or AB which gives you increased resistance to norovirus. And if you do get it, less severe symptoms.
What are your experiences?