Norovirus causes inflammation of the gastrointestinal tract.
Gastroenteritis , also known as infectious diarrhea , is inflammation of the gastrointestinal tract that involves the stomach and small intestine . Norovirus , sometimes referred to as the winter vomiting bug in the UK and Ireland , is the most common cause of viral gastroenteritis in humans . The species causes approximately 90 % of epidemic nonbacterial outbreaks of gastroenteritis around the world , and may be responsible for 50 % of all foodborne outbreaks of gastroenteritis in the United States .