Gastroenteritis is an infection of the bowel or irritation of the digestive tract, which is often caused by bacterial, viral or parasitic infections. It can affect people of all ages but is more common in young children. Depending on the causes of an ailment, the symptoms may appear within a few days of infection. They can either be severe or mild. The main symptoms of gastroenteritis include- diarrhoea, nausea and vomiting, mild fever and chills, abdominal pain or cramping, loss of appetite, fatigue and general body weakness, muscle aches and headache, loss of control over bowel motions and blood in your stools. These symptoms usually last for a day or two, but may also persist for up to a week. A doctor should be consulted if the symptoms do not improve after 5 days and after 2 days for children.