Gastroenteritis is inflammation of the gastrointestinal tract resulting in acute diarrhea. The inflammation is caused most often by infection with certain viruses, less often by bacteria or their toxins, parasites, or adverse reaction to something in the diet or medication. Worldwide, inadequate treatment of gastroenteritis kills 5 to 8 million people per year, and is a leading cause of death among infants and children under 5. At least 50% of cases of gastroenteritis as foodborne illness are due to norovirus. Risk factors are consumption of improperly prepared foods or contaminated water and travel or residence in areas of poor sanitation. Persons with rs601338(A;A) are immune to norovirus.