What is the difference between Stomach upset and Stomach flu?

Stomach upset usually means cramps, nausea, and vomiting and would more accurately be called gastritis. If the symptoms involve the intestines with abdominal cramps and diarrhea, then this is enteritis. Stomach upset might also come from indigestion or dyspepsia while the stomach flu can be called gastroenteritis.

Stomach flu is a short-lived stomach disorder of an unspecified cause. It can often be attributed to a virus. The stomach flu is usually caused by a virus that attacks the intestinal tract, which causes swelling and discomfort. Stomach upset, on the other hand, is generally accompanied by eating too quickly, eating fried or fatty foods, or overeating. The symptoms of stomach discomfort tend to be more predictable and less intense compared to the stomach flu.