The presence of viruses in recreational water can present a risk for human health and wastewater effluent is a source of virus in the environment. Their persistence in the environment influences their probability to find a new host. Studies have shown that external stressors can select for viruses that are more persistent under these stress conditions. The goal of this PhD was to understand how wastewater treatment and exposure to the environment modifies the community composition of enteroviruses in the water. It assessed specifically the effect of activated sludge and chlorination. The first step was to develop a method to measure the infectious concentration eight of the most abundant enterovirus genotypes in a wastewater sample. Using this method, the changes in population composition when going through activated sludge and chlorination were described. Finally, the diversity in environmental persistence of the enterovirus populations was assessed.

Overall, this thesis contributes to a better understanding of the variability of responses to sewage treatment and environmental exposure that exists among a population of enteroviruses. It highlights particularly persistent genotypes, and shows the importance of considering the diversity that exists among enterovirus genotypes when predicting the effect of an inactivating treatment or environmentally-associated stressor.