According to the Centers for Disease Control and Prevention (CDC), norovirus is the leading cause of vomiting and diarrhea, and foodborne illness in the United States. The agency also warns that infection with one type of norovirus may not protect an individual against other types., , , , Norovirus is a very contagious virus that spreads easily and quickly in different ways. To give an example, one can get norovirus by accidentally getting tiny particles of feces or vomit in their mouth from.