Chavarria Miró, GemmaAnfruns-Estrada, EduardMartínez-Velázquez, AdánVázquez Portero, MarioGuix Arnau, SusanaParaira, MiquelGalofré, BelénSánchez, GloriaPintó Solé, Rosa MaríaBosch, Albert2021-03-302021-10-012021-030099-2240https://hdl.handle.net/2445/175917Two large wastewater treatment plants (WWTP), covering around 2.7 M inhabitants, which represents around 85% of the metropolitan area of Barcelona, were sampled before, during and after the implementation of a complete lockdown. Five one-step RT-qPCR assays, targeting the polymerase (IP2 and IP4), the envelope E and the nucleoprotein (N1 and N2) genome regions, were employed for SARS-CoV-2 RNA detection in 24-h composite wastewater samples concentrated by polyethylene glycol (PEG) precipitation. SARS-CoV-2 was detected in a sewage sample collected 41 days ahead of the declaration of the first COVID-19 case. The evolution of SARS-CoV-2 genome copies in wastewater evidenced the validity of water-based epidemiology to anticipate COVID-19 outbreaks, to evaluate the impact of control measures and even to estimate the burden of shedders, including presymptomatic, asymptomatic, symptomatic and undiagnosed cases. For this latter objective, a model was applied for the estimation of the total number of shedders, evidencing a high proportion of asymptomatic infected individuals. In this way, an infection prevalence of 2.0-6.5% was figured. On the other hand, a proportion of around 0.12% and 0.09% of the total population was determined to be required for positive detection in the two WWTPs. At the end of the lockdown, SARS-CoV-2 RNA apparently disappeared in the WWTPs but could still be detected in grab samples from four urban sewers. Sewer monitoring allowed for location of specific hot spots of COVID-19, enabling the rapid adoption of appropriate mitigation measures.9 p.application/pdfeng(c) American Society for Microbiology, 2021SARS-CoV-2COVID-19Aigües residualsBarcelona (Catalunya : Àrea metropolitana)SARS-CoV-2COVID-19SewageBarcelona (Catalonia : Metropolitan area)info:eu-repo/semantics/article7064402021-03-30info:eu-repo/semantics/openAccess