A highly contagious stomach bug is creeping across Canada, wreaking gastrointestinal distress. Norovirus, like the Norwalk strain, is starting to cause major outbreaks this season bringing with it unpleasant symptoms linked to stomach flu, fever and fatigue. Infections usually spread in the colder months through contaminated food and can last for several days. If you or a friend feel the onset of an upset stomach, here's what you should keep in mind.