The presence of SARS-CoV-2 RNA in different freshwaters of urban settings determined by RT-qPCR: implications for water safety

Abstract

This is the first study focused on the presence of SARS-CoV-2 in different freshwater environments of an urban setting. Groundwater and surface water reservoirs for drinking water as well as water from receiving rivers of Monterrey Metropolitan Area were sampled repeatedly during a peak phase between October 2020 and January 2021, and the virus RNA was measured by quantitative reverse transcription polymerase chain reaction. Forty-four percent of groundwater samples demonstrated detectable virus loads between 2.9 and 5.6 copies/ml. A significant correlation with sucralose concentration in groundwater reaffirmed the hypothesis of leaching and infiltration of effluents from surface and/or failing sewage pipes, and emphases the importance of water disinfection. Thirteen percent of surface water dam samples tested positive, with values varying between 3.3 and 3.8 copies/ml. Finally, 21% of river samples marked positive for viral RNA, with concentrations ranging from 0.3 to 7.0 copies/ml. Raw wastewater samples taken in the same period show viral loads of up to 3535 copies/ml, demonstrating a dilution effect and/or efficiency of wastewater facilities. Variations of viral loads over time and at sub-metropolitan level in groundwater and surface water in general reflects the reported variation of infections for Monterrey.