A wastewater-based epidemiology tool for COVID-19 surveillance in Portugal

Sílvia Monteiro*, Daniela Rente, Mónica V. Cunha, Manuel Carmo Gomes, Tiago A. Marques, Artur B. Lourenço, Eugénia Cardoso, Pedro Álvaro, Marco Silva, Norberta Coelho, João Vilaça, Fátima Meireles, Nuno Brôco, Marta Carvalho, Ricardo Santos

*Corresponding author for this work

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The presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in wastewater produced interest in its use for sentinel surveillance at a community level and as a complementary approach to syndromic surveillance. With this work, we set the foundations for wastewater-based epidemiology (WBE) in Portugal by monitoring the trends of SARS-CoV-2 RNA circulation in the community, on a nationwide perspective during different epidemiological phases of the pandemic. The Charité assays (E_Sarbecco, RdRP, and N_Sarbecco) were applied to monitor, over 32-weeks (April to December 2020), the dynamics of SARS-CoV-2 RNA at the inlet of five wastewater treatment plants (WWTP), which together serve more than two million people in Portugal. Raw wastewater from three Coronavirus disease 2019 (COVID-19) reference hospitals was also analyzed during this period. In total, more than 600 samples were tested.

For the first weeks, detection of SARS-CoV-2 RNA was sporadic, with concentrations varying from 103 to 105 genome copies per liter (GC/L). Prevalence of SARS-CoV-2 RNA increased steeply by the end of May into late June, mainly in Lisboa e Vale do Tejo region (LVT), during the reopening phase. After the summer, with the reopening of schools in mid-September and return to partial face-to-face work, a pronounced increase of SARS-CoV-2 RNA in wastewater was detected. In the LVT area, SARS-CoV-2 RNA load agreed with reported trends in hotspots of infection. Synchrony between trends of SARS-CoV-2 RNA in raw wastewater and daily new COVID-19 cases highlights the value of WBE as a surveillance tool, particularly after the phasing out of the epidemiological curve and when hotspots of disease re-emerge in the population which might be difficult to spot based solely on syndromic surveillance and contact tracing. This is the first study crossing several epidemiological stages highlighting the long-term use of WBE for SARS-CoV-2.
Original languageEnglish
Article number150264
Number of pages10
JournalScience of the Total Environment
Early online date11 Sept 2021
Publication statusPublished - 15 Jan 2022


  • SARS-CoV-2
  • Wastewater-based epidemiology
  • COVID-19
  • Hospital wastewater


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