An upset stomach can be a result of many things. When symptoms include vomiting, diarrhea and fever, chances are it’s a viral infection. “A viral gastroenteritis, which we sometimes call ‘a stomach bug’ or ‘a stomach flu,” is a common reason for having an acute onset of vomiting and diarrhea, and sometimes with fever,” says Dr. Tina Ardon, a Mayo Clinic family medicine physician. The viral infection is most commonly...