The stomach virus is actually not caused by the influenza virus. It's an intestinal infection. You can get sick from parasites, toxins, bacteria, and viruses. u003cbr/u003eu003cbr/u003eViruses are the most common cause of stomach flu. The Norovirus is often the culprit for adults. The Rotavirus is often to blame for the stomach bug in children. These viruses make your stomach and intestines irritated and inflamed.