Noro is the most common cause of gasto at 36%.. rota virus would be a very close second.. In that remainder 64% you have got things like : Food allergies, improper diet, food poisening, excessive alcohol or tobacco can lead to gastroenteritis, viral infections, bacterial infections, intestinal parasites and stress and certain types of medication..
ALL of these come under different types of gastroenteritis believe it or not.

But if you think about it, if u take noro out of the equasion then there is not that much to worry about, most of us dont drink excessivley, most of us are peticular with what we eat so that rules out food poisening, intestinal parasites are from raw or undercooked meat or dirty drinking water so i think we are realtivley safe.. the only other worry is rota virus which is mild in adults anyway.

Just my view on it tho x