Persistence of Human Respiratory Viral RNA in Wastewater Settled Solids

Wastewater-based epidemiology has emerged as a valuable tool for monitoring respiratory viral diseases within communities by analyzing concentrations of viral nucleic-acids in wastewater. However, little is known about the fate of respiratory virus nucleic-acids in wastewater. Two important fate processes that may modulate their concentrations in wastewater as it moves from household drains to the point of collection include sorption or partitioning to wastewater solids and degradation. This study investigated the decay kinetics of genomic nucleic-acids of seven human respiratory viruses, including SARS-CoV-2, RSV, HCoV-OC43, HCoV-229E, HCoV-NL63, HRV, and IAV, as well as PMMoV in wastewater solids. Viruses were spiked into wastewater solids and their concentrations were followed for 50 days at three different temperatures (4, 22, and 37 °C). Viral genomic RNA decayed following first order kinetics with decay rate constants k from 0 to 0.219 per day. Decay rate constants were not different from 0 for all targets in solids incubated at 4°C, and were largest at 37°C, rate constants were similar across nucleic-acid targets. Regardless of temperature, there was limited viral RNA decay, with estimated 0 to 20% reduction, over the typical residence times of sewage in the piped systems between input and collection point (<1 day). The k values reported herein can be used directly in fate and transport models to inform the interpretation of measurements made during wastewater surveillance.