Norovirus is a highly contagious virus that causes gastroenteritis, leading to inflammation of the stomach and intestines. Symptoms typically include nausea, vomiting, diarrhea, and abdominal cramps, often appearing suddenly and lasting for one to three days. It spreads easily through contaminated food, water, surfaces, and close contact with infected individuals. Due to its resilient nature, norovirus outbreaks can occur in crowded environments such as schools, cruise ships, and nursing homes.