Probabilistic models for Risk assessment of viral infection associated with contaminated food consumption : public health impact of norovirus or hepatitis A virus contamination in oysters ; Modélisations probabilistes du risque d’infection virale associé à la consommation d’aliments contaminés : impact pour la santé publique de la contamination d’huîtres par Norovirusou par le virus de l’Hépatite A

Novirus (NoV) and hepatitis A virus (HAV) are most important foodborne viruses considering morbidity and mortality disease burden. The main transmission pathways of these viruses is orofaecal, involving inter-human transmission. Contaminated shellfish are identified as an important source of human viral outbreaks in France. The study of a coastal situation allow to explore complete faeco –oral pathway. The aim work is to estimate the risk of infection for a coastal population of oyster contamination by HAV and NoV and to evaluate the effect of some mitigation strategies. Quantitative risk assessment (QRA), showed the benefit of reducing the contamination of marine waters and of viral monitoring. The dose-response parameters were estimated for GII and GI, based on shellfish outbreaks data, with bayesian inference. Infectivity of Nov GI and GII for secretors and non secretors was seen to be high. QRA approach was included into a stochastic compartmental dynamic model for NoV.The aim of this model was to estimate the global health impact of closure of shellfish area, with two ways of transmission (by food and inter-human), whenever a winter epidemic occurs with GI or GII or both. First results are indicating the potential interest of closure of the area, and the main importance of food transmission for GI cases. This work show the benefit of QRA for estimating foodborne cases but also dynamic modeling involving foodborne pathway for humans. ; Norovirus (NoV) et le virus de l'hépatite A (VHA) ont le cout sanitaire par voie alimentaire en terme de morbidité et de mortalité le plus élevé. Ces virus, dont la voie de transmission est orofécale, se transmettent aussi par une voie interhumaine. L'ingestion de coquillages contaminés constituent une source de cas groupés fréquente pour VHA et NoV en france. L'objectif de cette thèse est d'évaluer le risque lié à la consommation de coquillages contaminé par VHA ou NoV et d'évaluer l'efficacité de quelques mesures de gestion pour une population côtière, par une modélisation ...