Sometimes it's called "food poisoning" or "stomach flu" or just simply the "runs." It's caused by a group of viruses (noroviruses) that affect the gastrointestinal tract and cause inflammation. This gastroenteritis is not pleasant to experience, but usually lasts only a day or two. There is a new strain causing 60% of U.S. outbreaks--GII.4 Sydney. It spreads very quickly via contact from infected people, contaminated food, or objects.
PositiveTip: Limit your risk of norovirus infection by washing your hands carefully with soap and water often.