Question: how long can you have gastro before symptoms?
Answer: Gastroenteritis symptoms usually begin 1 to 2 days after you have taken in the germ, but it can be as early as 1 hour (for example staphylococcal toxin) and as long as 60 days (for example Listeria infection). Symptoms can include: nausea and/or vomiting. diarrhoea, sometimes containing blood.