Norwalk viruses are more commonly associated with outbreaks of gastroenteritis in nursing homes, homes for the aged and adult institutions. Enteric outbreaks in children's facilities like hospitals, daycares and hospital nurseries are more commonly caused by a Rotavirus. However both can be the causative agent in outbreaks of vomiting and diarrhea in both age groups. Both these viral conditions can occur year round.
Incidence is higher in the fall and winter.
Norwalk induced gastroenteritis is usually a self-limiting, mild to moderate disease. Clinical symptoms include nausea, vomiting, diarrhea, abdominal pain, headache, malaise, low grade fever or a combination of these symptoms. Gastrointestinal symptoms usually last 24 to 48 hours. Man is the only known reservoir. Mode of transmission is not definitely known.