Some people experience gastrointestinal symptoms such as nausea, vomiting, stomach cramps and diarrhea. These symptoms occur because of increased body temperature and the viral damage done to the epithelium of the intestines. Although quite unpleasant, these symptoms are rarely severe. Keep in mind that children are particularly sensitive to body fluid changes due to diarrhea and vomiting. Oral rehydration therapy or even in-hospital dehydration treatment may be needed. Typically, gastrointestinal symptoms develop quickly (sudden diarrhea, for example) and subside after 1 or 2 days.