Gastro is an illness which may cause some or all of the following symptoms: • diarrhoea • stomach cramps • vomiting • nausea • fever • headache Germs which cause gastro get into your body through your mouth and it usually takes several days for symptoms to appear. This time is known as the incubation period. Sometimes symptoms may occur within hours of the germs entering your body but it is usually longer. When people get gastro they often assume that the last meal they ate gave them food poisoning. This is usually not the case.