A stomach bug can knock you off your feet fast. One moment you feel fine, and the next you are dealing with nausea, vomiting, or diarrhea that leaves you wondering how long you need to isolate yourself from others. Because stomach bugs spread so easily in households, schools, and workplaces, knowing when you are contagious can help you protect the people around you. Stomach bugs, also known as viral gastroenteritis, are usually caused by viruses ...