Spatiotemporal Surveillance of SARS-CoV-2 in Wastewater: Comparative Analysis of Viral Loads in Sewer and Treatment Plant Samples from Las Heras, Mendoza, Argentina (2020–2025)

Abstract

Wastewater-Based Epidemiology (WBE) has emerged as a critical tool for monitoringSARS-CoV-2 circulation at the community level. This study assessed spatiotemporal viraldynamics in Las Heras, Mendoza, Argentina, by comparing wastewater samples fromsix sewer maintenance holes and three wastewater treatment plants (WWTPs) betweenJanuary and June 2021, and by conducting long-term surveillance at Campo Espejo WWTPduring epidemic (2020–2021) and endemic (2024–2025) phases of COVID-19. Viral particlesfrom sewer manholes and WWTPs samples were concentrated by polyethylene glycolprecipitation or aluminum polychloride adsorption–precipitation methods, and then SARSCoV-2 RNA was quantified by reverse transcription quantitative polymerase chain reactiontargeting N1 and N2 nucleocapsid viral markers. Results showed consistent detection ofviral RNA across all sites, with peaks in wastewater preceding diagnosed COVID-19 casesincreases, confirming WBE as an early-warning system. Localized sewer sampling identified urban hotspots, while WWTPs monitoring captured broader epidemiological trends.Recently, COVID-19 surveillance showed lower and intermittent viral loads, decoupledfrom diagnosed cases, compared to epidemic phase, indicating a transition to endemiccirculation. Overall, combining upstream and downstream WBE enhanced spatial andtemporal resolution, demonstrating its utility for public health monitoring during bothepidemic and endemic phases.