Diarrhoea is often the result of a viral, bacterial or other type of infection. Diarrhea is most commonly caused by rotaviruses. For mild diarrhea, it is often enough to simply drink plenty of fluids so you do not dehydrate, and wait for it to run its course. Diarrhea is quite common in babies and toddlers. Very severe diarrhea can result in the loss of dangerously large amounts of fluids. Because of this, medical treatment is needed for severe diarrhea — especially when it affects small children or older people. Symptoms Someone is considered to have diarrhea if they have very loose or watery stools three or more times within 24 hours. Other symptoms may include bellyache and bloating (gas). Infections that can cause diarrhea sometimes also lead to nausea and vomiting.