Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The norovirus infection, also known as the Norwalk agent, is a viral illness, caused by an RNA virus, responsible for more than 90% of cases of gastroenteritis outbreaks worldwide. Having no vaccine, the norovirus is highly contagious and spreads rapidly from person to person, via contaminated food, water, objects, surfaces or virus aerosol spread, in environments such as, hospitals, nursing homes, day care centers etc. Despite the numerous preventive measures taken, many cases of the norovirus outbreaks occur on cruise ships, learning centers, education institutions, schools, colleges and other crowded places. Learn more about the norovirus infection, its history, prevention and mechanism of action in this book.