Tonight, i am dealing with a low grade fever and diarrhea. im staying with a friend and im terrified im going to give it to her / dont know if i have something contagious. how do i know if its noro or something i can give to her?

Very hard to tell: Contagiousness varies among different "stomach viruses" and among different people, so is not easily predictable. However, one can feel safer if the sick person wakes up on Day 5 without any symptoms the preceding 4 days. If unlucky, she can still catch a virus and come down with the illness. Food poisoning is usually less contagious, but depends on the bacteria type.