 This is a prospective, open label, cluster randomized trial of 2 880 expected patients who calling a French emergency medical service Dial 15 for fever or gastroenteritis symptoms during out-of-hours periods. All calls will be taken by a general practitioner GP. Out-of-hours period is defined as 8 PM to 8 AM on weekdays, 1 PM to 8PM on Saturdays in addition to Sundays and holidays.To be exhaustive, we will enrol patients during one year. 