Viral gastroenteritis is commonly referred to as the 'stomach flu'. But it is not caused by influenza, the respiratory virus that causes the flu. The most common cause of stomach flu is the microorganisms spread in water and food that usually cause infections. This virus mostly infects the lining of the small intestine. The infection can also be transmitted from one person to another, but it is more likely to occur in a place where many people share places to stay or eat. Common symptoms such as watery, usually non-bloody diarrhea. Abdominal cramps and pain nausea, vomiting or both, occasional muscle aches or headaches, fever. etc. are seen.