Norovirus is a very contagious virus. You can get Norovirus from contaminated food or water, or an infected person or by touching contaminated surfaces. The virus causes your stomach or intestines or both to get inflamed (acute gastroenteritis). This leads you to have stomach pain, nausea, and diarrhea and to throw up. Anyone can be infected with Norovirus and get sick. Also, you can have Norovirus illness many times in your life. Norovirus illness can be serious, especially for young children and older adults.