Gastroenteritis is an infection in the stomach and intestines that causes diarrhea and sometimes vomiting. It is common in babies and children. It is caused by a virus or bacteria in the intestinal tract (bowels). Bacteria or viruses get to the intestinal tract by putting hands, toys or other objects near or into the mouth.

It is more serious in babies and young children than it is in adults because the diarrhea can cause dehydration. Vomiting can also cause the loss of important minerals from the body (dehydration).