Comparative Inactivation of the RNA of the Delta and Omicron Variants of SARS-CoV-2 in Wastewater of Five Municipalities in Southeast Germany

Abstract

During the COVID-19 pandemic, wastewater-based epidemiology has been extensively used as a helpful tool for evaluation of the epidemic situation in catchments of wastewater treatment plants. In this context, knowledge about the rate of virus inactivation in wastewater is important for characterization of the influence of retention times in sewers on virus concentrations, of the storage periods before analysis in the laboratory, on virus elimination during treatment and for modeling approaches. In the present study, we genotyped SARS-CoV-2 in the respiratory tract specimens of infected patients and spiked the raw wastewater of five treatment plants with aliquots of these samples. The test preparations were incubated under practically relevant temperature conditions (14 °C) over 31 days. The linear decay rates resulted in comparable T90 values (30.5 d) for the Delta and the Omicron BA1 variants of SARS-CoV-2 without differences in using the E or S gene of the virus as the target for amplification. In contrast, the origin of wastewater influenced the inactivation rate of both variants significantly, with the mean T90 values varying between 24.3 and 53.1 days in the wastewater from the five plants. The data suggest that the inactivation rate of SARS-CoV-2 in wastewater is more strongly determined by the composition of the water than by the virus variant.