Number of COVID-19 cases required in a population to detect SARS-CoV-2 RNA in wastewater in the province of Alberta, Canada: Sensitivity assessment

With a unique and large size of testing results of 1,842 samples collected from 12 wastew-ater treatment plants (WWTP) for 14 months through from low to high prevalence of COVID-19, the sensitivity of RT-qPCR detection of SARS-CoV-2 RNA in wastewater that cor-respond to the communities was computed by using Probit analysis. This study determined the number of new COVID-19 cases per 100,000 population required to detect SARS-CoV-2 RNA in wastewater at defined probabilities and provided an evidence-based framework of wastewater-based epidemiology surveillance (WBE). Input data were positive and negative test results of SARS-CoV-2 RNA in wastewater samples and the corresponding new COVID-19 case rates per 100,000 population served by each WWTP. The analyses determined that RT-qPCR-based SARS-CoV-2 RNA detection threshold at 50%, 80% and 99% probability re-quired a median of 8 (range: 4-19), 18 (9-43), and 38 (17-97) of new COVID-19 cases /100,000, respectively. Namely, the positive detection rate at 50%, 80% and 99% probability were 0.01%, 0.02%, and 0.04% averagely for new cases in the population. This study improves under-standing of the performance of WBE SARS-CoV-2 RNA detection using the large datasets and prolonged study period. Estimated COVID-19 burden at a community level that would result in a positive detection of SARS-CoV-2 in wastewater is critical to support WBE applica-tion as a supplementary waming/monitoring system for COVID-19 prevention and control.(c) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Automated summary

By analyzing a large dataset of 1,842 samples collected from 12 wastewater treatment plants over a period of 14 months, this study used Probit analysis to calculate the sensitivity of RT-qPCR detection of SARS-CoV-2 RNA in wastewater. It determined the number of new COVID-19 cases required to detect the virus in wastewater at different probabilities and provided an evidence-based framework for wastewater-based epidemiology surveillance. The study improves our understanding of the performance of SARS-CoV-2 RNA detection in wastewater using extensive data and a prolonged study period. It highlights the importance of estimating the COVID-19 burden that will result in positive detection in wastewater for the application of wastewater-based surveillance as a supplementary system for COVID-19 prevention and control.