The symptoms you feel are caused by your body fighting the viruses. Fever is your body heating up to try to overheat and kill the virus. Vomit/Diarrhea is your body getting rid of whatever you ate via the nearest exit, mouth/butt. Snot, sneezing, etc is your sinus creating a mucus layer of protection to try and catch and remove the illness. Coughing is when that mucus makes it into your lungs.