This Centers for Disease Control and Prevention webpage provides information and resources on Norovirus. "Norovirus is a very contagious virus. You can get norovirus from an infected person, contaminated food or water, 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. Norovirus is the most common cause of acute gastroenteritis in the United States. Each year, it causes about 21 million illnesses and contributes to about 70,000 hospitalizations and 800 deaths. Norovirus is also the most common cause of foodborne-disease outbreaks in the United States."
Centers for Disease Control and Prevention: http://www.cdc.gov/