Have you or your family recently been ill with vomiting and diarrhea? There is a good chance it was caused by a norovirus, commonly called "the stomach flu." Noroviruses are highly contagious viruses that cause nausea, vomiting, diarrhea and abdominal cramping. Some people also experience headache, low grade fever, and body aches. Symptoms usually last for 24 to 48 hours. See our fact sheet for more information.