However, older children and adults also can get sick from rotavirus. Once a person has been exposed to rotavirus, it takes about 2 days for the symptoms to appear. Children who get infected may have severe watery diarrhea, often with vomiting, fever, and abdominal pain. Vomiting and watery diarrhea can last from 3 to 8 days. Additional symptoms may include loss of appetite and dehydration (loss of body fluids), which can be especially dangerous for infants and young children. Symptoms of dehydration include.