Symptoms of a stomach bug or flu typically last from one to three days, according to WebMD, though they may last longer in some cases. Healthline indicates that some forms of stomach viruses may show symptoms for up to 10 days. Cramps, diarrhea and vomiting are the most severe symptoms.
Stomach bugs typically aren't serious, though there are risks of dehydration, WebMD states. Infants and the elderly face greater risks from stomach bugs. Nausea, headaches, fevers and sore muscles are other possible symptoms with a stomach virus, according to Healthline. Drinking plenty of fluids while symptoms persist is important to protect against dehydration.