What causes diarrhea and/or vomiting?
Many different germs can cause gastroenteritis, including viruses (such as rotaviruses, noroviruses [Norwalk virus]), bacteria (such as Salmonella or Shigella), and parasites (such as Giardia). Medications and certain medical conditions can also cause similar symptoms. A doctor can determine if the diarrhea is caused by a germ or by something else.