norovirusDoctors call it "acute gastroenteritis." To many other people, it’s "stomach flu" (though real influenza is a respiratory, not digestive, illness). Whatever you call it, a sudden illness involving diarrhea, vomiting or both is a miserable thing. And occasionally — as demonstrated by the recent deaths linked to E. coli-tainted spinach — it can be a dangerous thing.

But, as USA Today printed in an article today, in the words of Chesapeake, Va., gastroenterologist Patricia Raymond: "The GI (gastrointestinal) tract has a limited palette of expression. You vomit, you cramp, you have diarrhea."

So how do you tell a really bad bug from one that is merely unpleasant? How do you tell one that came from food from one you picked up from a doorknob or a baby’s diaper? In short, when should you worry?

Usually, doctors say, both worry and detective work are unnecessary: Whether the culprit is viral or bacterial, food-borne or not, you’ll most likely recover in a couple of days and won’t need medical attention. If you suspect the Thanksgiving stuffing, it’s nice to let other family members know. And you should change your cooking habits (or your caterer). But there’s rarely a need to send the whole clan in for a battery of tests and treatments.