Shellfish filter large volumes of water to meet their nutritional needs, thereby ingesting phytoplankton, but they also concentrate microorganisms naturally present in the water (vibrio bacteria, phycotoxins) or those of fecal origin discharged into the sea via waterways (enteric viruses, enterobacteria, protozoa). Analysis of data from systems contributing to the surveillance of foodborne illnesses linked to shellfish consumption and published outbreak investigations shows that, in France, foodborne illnesses linked to shellfish consumption are primarily of viral origin, mainly due to noroviruses and secondarily to the hepatitis A virus (HAV). The risk associated with phycotoxins appears low, and that associated with enterobacteria and vibrios very low. Mandatory reporting (MR) of foodborne illnesses remains the most effective system for monitoring and detecting health effects linked to shellfish consumption. This MR could be strengthened in shellfish-producing areas, on the one hand by increasing its comprehensiveness through awareness-raising among potential reporters in the monitored area, and on the other hand by increasing the number and quality of investigations. In terms of prevention, environmental and shellfish monitoring systems tailored to phycotoxin and bacteriological risks could be supplemented by a preventive approach to fecal contamination, based primarily on securing sanitation systems and sharing warning signals among partners to suspect or anticipate environmental contamination, so that shellfish farmers can implement protective measures for their shellfish. (R.A.)