Population Infection Estimation from Wastewater Surveillance for SARS-CoV-2 in Nagpur, India During the Second Pandemic Wave

Background: Wastewater-based epidemiology (WBE) has emerged as an effective environmental surveillance tool for predicting SARS-CoV-2 disease outbreaks in high-income countries (HICs) with centralized sewage infrastructure. However, few studies have applied WBE alongside epidemic disease modelling to estimate the prevalence of SARS-CoV-2 in low-resource settings. The aim of this study was to explore the feasibility of collecting untreated wastewater samples from rural and urban catchment areas of Nagpur district, to detect and quantify SARS-CoV-2 using real-time qPCR, to compare geographic differences in viral loads, and to integrate the wastewater data into a modified Susceptible-Exposed-Infectious-Confirmed-Positives-Recovered (SEIPR) model. Findings: Of the 983 wastewater samples analyzed for SARS-CoV-2 RNA, we detected significantly higher sample positivity rates 43·7% (95% confidence interval (CI) 40·1, 47·4) and 30·4% (95% CI 24·66, 36·66), and higher viral loads for the urban compared with rural samples, respectively. Basic reproductive number, R0, positively correlated with population density and negatively correlated with humidity, a proxy for rainfall and dilution of waste in the sewers. The SEIPR model estimated the rate of unreported coronavirus disease 2019 (COVID-19) cases at the start of wave as 13·97 [95% CI (10·17, 17·0)] times that of confirmed cases, representing a material difference in cases and health care resource burden. Interpretation: Surveillance from wastewater may be a more protective way for healthcare authorities to prepare for surges in COVID-19 cases during future waves. Funding: Global Challenges Research Fund, Research England, UKRIDeclaration of Interests: The authors declare no conflict of interest, financial or otherwise.Ethics Approval: The study was approved by Faculty of Medicine and Health Sciences Research Ethics Committee at the University of Nottingham (REC No. 131-1120), and the institutional ethics committees of the Central India Institute of Medical Sciences, Nagpur, and Dr B. Lal Institute of Biotechnology, Jaipur.