How long does gastroenteritis remain contagious?

Up to 3 weeks: Rotavirus, the most common cause of gastroenteritis, is shed in the stool for up to 21 days. Obviously most kids are not excluded from daycare that long after an illness, which is why hand hygiene is so important.

Depends on the cause: Most pathogens which cause gastroenteritis are viral. Viruses which cause gastroenteritis can be infectious from several days up to a few weeks. In general, once you are no longer having symptoms, you are no longer contagious. Hope this helps!