Infectious gastroenteritis
Gastroenteritis is an inflammation of the lining of the intestines caused by a virus, bacteria or parasites. Viral gastroenteritis is the second most common illness in many countries. The cause is often a norovirus infection. It spreads through contaminated food or water, and contact with an infected person. The best prevention is frequent hand washing.
Organs of digestive tract
Symptoms of gastroenteritis include diarrhea, abdominal pain, vomiting, headache, fever and chills. Most people recover with no treatment.
The most common problem with gastroenteritis is dehydration. This happens if you do not drink enough fluids to replace what you lose through vomiting and diarrhea. Dehydration is most common in babies, young children, the elderly and people with weak immune systems.
Source: http://www.nlm.nih.gov/medlineplus/gastroenteritis.html