Results from the SARS-CoV-2 wastewater-based surveillance system in Denmark, July 2021 to June 2022.
Lene Wulff Krogsgaard, Guido Benedetti, Aina Gudde, Stine Raith Richter, Lasse Dam Rasmussen, Sofie Elisabeth Midgley, Amanda Gammelby Qvesel, Maarten Nauta, Naja Stolberg Bahrenscheer, Lene von Kappelgaard, Oliver McManus, Nicco Claudio Hansen, Jan Bryla Pedersen, Danny Haimes, Jesper Gamst, Louise Solveig Nørgaard, Alissa Carina Udi Jørgensen, Ditte Møller Ejegod, Simone Skjødt Møller, Jes Clauson-Kaas, Ida Marie Knudsen, Kristina Træholt Franck, Steen Ethelberg
Author Information
Lene Wulff Krogsgaard: Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark.
Guido Benedetti: Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark. Electronic address: gube@ssi.dk.
Aina Gudde: Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark.
Stine Raith Richter: Department of Virus and Microbiological Special Diagnostics, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark.
Lasse Dam Rasmussen: Department of Virus and Microbiological Special Diagnostics, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark.
Sofie Elisabeth Midgley: Department of Virus and Microbiological Special Diagnostics, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark.
Amanda Gammelby Qvesel: Department of Virus and Microbiological Special Diagnostics, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark.
Maarten Nauta: Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark.
Naja Stolberg Bahrenscheer: Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark.
Lene von Kappelgaard: Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark.
Oliver McManus: Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark; European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Prevention and Control, Gustav III: s Boulevard 40, 16973 Solna, Sweden.
Nicco Claudio Hansen: Test Centre Denmark, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark.
Jan Bryla Pedersen: Department of Finance, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark.
Ida Marie Knudsen: HOFOR - Greater Copenhagen Utility, Ørestads Boulevard 35, 2300 Copenhagen, Denmark.
Kristina Træholt Franck: Department of Virus and Microbiological Special Diagnostics, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark.
Steen Ethelberg: Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark; Department of Public Health, Global Health Section, University of Copenhagen, Øster Farimagsgade 5, 1014 Copenhagen, Denmark.
The microbiological analysis of wastewater samples is increasingly used for the surveillance of SARS-CoV-2 globally. We described the setup process of the national SARS-CoV-2 wastewater-based surveillance system in Denmark, presented its main results during the first year of activities, from July 2021 to June 2022, and discussed their operational significance. The Danish SARS-CoV-2 wastewater-based surveillance system was designed to cover 85 % of the population in Denmark and it entailed taking three weekly samples from 230 sites. Samples were RT-qPCR tested for SARS-CoV-2 RNA, targeting the genetic markers N1, N2 and RdRp, and for two faecal indicators, Pepper Mild Mottle Virus and crAssphage. We calculated the weekly SARS-CoV-2 RNA concentration in the wastewater from each sampling site and monitored it in view of the results from individual testing, at the national and regional levels. We attempted to use wastewater results to identify potential local outbreaks, and we sequenced positive wastewater samples using Nanopore sequencing to monitor the circulation of viral variants in Denmark. The system reached its full implementation by October 2021 and covered up to 86.4 % of the Danish population. The system allowed for monitoring of the national and regional trends of SARS-CoV-2 infections in Denmark. However, the system contribution to the identification of potential local outbreaks was limited by the extensive information available from clinical testing. The sequencing of wastewater samples identified relevant variants of concern, in line with results from sequencing of human samples. Amidst the COVID-19 pandemic, Denmark implemented a nationwide SARS-CoV-2 wastewater-based surveillance system that integrated routine surveillance from individual testing. Today, while testing for COVID-19 at the community level has been discontinued, the system is on the frontline to monitor the occurrence and spread of SARS-CoV-2 in Denmark.
