Noroviruses are a group of viruses (previously known as Norwalk-like viruses) that can cause gastroenteritis, an inflammation of the stomach and intestines. Norovirus is the leading cause of foodborne illness outbreaks in Minnesota. This infection is often mistakenly referred to as the “stomach flu”. Norovirus is not related to the flu (influenza), which is a common respiratory illness caused by the influenza virus. Common symptoms of norovirus infection include vomiting, diarrhea, and stomach cramping. Less common symptoms can include low-grade fever or chills, headache, and muscle aches. Symptoms usually begin 1 or 2 days after ingesting the virus, but may appear as early as 12 hours after exposure.