Technical framework for wastewater-based epidemiology of SARS-CoV-2 based on relative quantification via qPCR

The global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has greatly affected people’s normal production, living, social and economic activities. Wastewater-based epidemiology (WBE) is expected to become a powerful tool to monitor the dissemination of SARS-CoV-2 at the community level, which has attracted the attention of scholars all over the world. However, there is not yet a standard protocol to guide its implementation. In this paper, we attempt to propose a technical framework of relative quantification for determining the virus abundance in wastewater and estimating the infection rate in corresponding communities, which is expected to achieve horizontal and vertical comparability in virtue of human-specific biomarkers as internal references. A comprehensive theoretical framework for relative quantification of viruses by qPCR is provided and discussed in detail. Critical factors affecting the virus detectability in wastewater and the estimation of infection rate include virus concentration methods, lag-period, per capita virus shedding amount, sewage generation rate, temperature-related decay kinetics of virus/biomarkers in wastewater, and hydraulic retention time (HRT), etc. Theoretical simulation shows that the main factors affecting the detectability of virus in sewage are per capita virus shedding amount and sewage generation rate. While the decay of SARS-CoV-2 in sewage is a relatively slow process, which has limited impact on its detection. Under the ideal condition of high per capita virus shedding amount and low sewage generation rate, WBE can give early warning for single infected person among 400,000 people.