Every day, local health departments field calls from customers complaining about having the “24-Hour Flu” or “The Stomach Flu.” In truth, the cause of most of these cases is Norovirus. The person calling generally blames the last food they ate for making them sick. It usually isn’t the last meal eaten that made them sick, rather it is something they had within the past few days. The average incubation, or the time it takes for symptoms to manifest, is generally 24-72 hours.