The gathering organized by the "Vie et Lumière" evangelical mission is a religious event that brings together members of the Protestant Romani community. For the past decade, this gathering has been held annually in Nevoy, in the Loiret department (45), on private property owned by the association. Health risks may be heightened during large gatherings of people, particularly due to: - the concentration of people at the same time and place, which can facilitate the spread of diseases with epidemic potential, - the establishment of temporary facilities, which are sometimes precarious (housing, food services), despite the health control measures put in place, - unusual environmental hazards (heatstroke, trauma). For this gathering, a health surveillance system was established at the initiative of the Loiret Departmental Directorate of Health and Social Affairs (DDASS), in collaboration with the Gien Hospital Center and with the support of the Center-West Interregional Epidemiology Unit (CIRE) and the Institute for Public Health Surveillance (InVS). The surveillance system was designed to rapidly detect any occurrence within the gathering that might warrant preventive, prophylactic, or public health control measures, and to guide interventions in the event of a potential epidemic. Certain diseases that could pose a threat to the population were subject to specific reporting requirements, notably: meningococcal meningitis, viral hepatitis A, exanthematous fevers, and gastroenteritis. Three sources provided daily data using a standardized collection method: the medical clinic set up specifically at the gathering site, and the emergency and pediatric departments of the Gien Hospital Center. Medical coverage at the clinic was provided by volunteer general practitioners and nurses seconded from the Gien Hospital Center. Data were analyzed within the day, and a report was issued daily. In total, 627 medical consultations were recorded across the three sources, in addition to 178 nursing care visits at the medical clinic. No epidemic was detected by the surveillance system. In particular, one case presenting with meningeal syndrome and one case of hepatitis A were treated. Additionally, a bacteriological and physiological water quality test was conducted by the Health and Environment Department of the DDASS. Analyses of samples taken at various points (collection, storage, and distribution) showed good bacteriological water quality for the parameters tested. Nevertheless, this gathering took place under precarious conditions in terms of hygiene. In this context, the integration of surveillance activities into the hosting framework appears to be an important complement to inspection and control activities. They enable health officials to be alerted and form the basis for essential collaboration in the event of an epidemic.