Stomach flu symptoms include diarrhea, vomiting, excessive urination and excessive sweating. These symptoms come together to result in large amounts of fluid loss, which can be very dangerous, especially for young children. Children are especially vulnerable to dehydration, and this is made worse by a tendency for those afflicted not to drink sufficient fluids because of nausea, a loss of appetite or difficulty swallowing. It is also common for children to complain of stomach ache, abdominal pain and stomach cramps.