Tracing the fate of wastewater viruses reveals catchment-scale virome diversity and connectivity

The discharge of wastewater-derived viruses in aquatic environments impacts catchment-scale virome composition. To explore this, we used viromic analysis of RNA and DNA virus-like particles to holistically track virus communities entering and leaving wastewater treatment plants and the connecting river catchment system and estuary. We reconstructed >40 000 partial viral genomes into 10 149 species-level groups, dominated by dsDNA and (+)ssRNA bacteriophages (Caudoviricetes and Leviviricetes) and a small number of genomes that could pose a risk to human health. We found substantial viral diversity and geographically distinct virus communities associated with different wastewater treatment plants. River and estuarine water bodies harboured more diverse viral communities in downstream locations, influenced by tidal movement and proximity to wastewater treatment plants. Shellfish and beach sand were enriched in viral communities when compared with the surrounding water, acting as entrapment matrices for virus particles. Extensive phylogenetic analyses of environmental-derived and reference sequences showed the presence of human-associated sapovirus GII in all sample types, multiple rotavirus A strains in wastewater and a diverse set of picorna-like viruses associated with shellfish. We conclude that wastewater-derived viral genetic material is commonly deposited in the environment and can be traced throughout the freshwater-marine continuum of the river catchment, where it is influenced by local geography, weather events and tidal effects. Our data illustrate the utility of viromic analyses for wastewater- and environment-based ecology and epidemiology, and we present a conceptual model for the circulation of all types of viruses in a freshwater catchment.