Norovirus is a highly contagious virus that causes gastroenteritis, an inflammation of the stomach and intestines. It is often referred to as the "stomach flu," although it is not related to the influenza virus. Symptoms typically include vomiting, diarrhea, stomach cramps, and nausea, which can start suddenly and last for one to three days. The virus spreads through contaminated food, water, surfaces, or close contact with infected individuals. Outbreaks commonly occur in crowded places like cruise ships, schools, and nursing homes. Good hygiene practices, such as frequent handwashing, can help prevent the spread of Norovirus.