National wastewater surveillance of SARS-CoV-2

The national wastewater surveillance of SARS-CoV-2 in Denmark covers 49% of the population. Wastewater samples are collected from 29 wastewater treatment plants distributed across the country, allowing the development of SARS-CoV-2 to be monitored both nationally and regionally.

SARS-CoV-2 status in wastewater as of 22.10.2025

In week 42 (October 13 - October 19) the national SARS-CoV-2 concentration in wastewater, indicating the amount of SARS-CoV-2 circulating in the population, is at a medium level.

In all five regions, the concentration is likewise at a medium level.

The national growth rate, which is the average weekly growth over the past three weeks (September 29 - October 19), shows a development in the SARS-CoV-2 wastewater concentration at 2% corresponding to the category "No growth".

National concentration of SARS-CoV-2 in wastewater over time and the current growth rate

The figure below shows the concentration levels of SARS-CoV-2 in wastewater across all sampling locations, as well as this week's growth rate.

The figure shows the development of the average concentration of SARS-CoV-2 in wastewater over the past 16 months. The concentration is adjusted according to the amount of feces in the wastewater to account for dilution and changes in the number of people contributing to the wastewater. The concentration is divided into five levels (very low, low, medium, high, and very high), which are marked as horizontal bands on the figure. The growth rate, which is the average weekly percentage change based on the most recent three weeks of measurements, can also be seen on the figure. The growth rate is indicated with colors and ranges from a very strong decrease to a very strong increase across a total of seven categories. The graph shows an increase from spring to late summer 2024, a clear peak around December 2024 and January 2025 at a medium level, followed by a decline to a very low level from February to June 2025. In July 2025, a new increase to the medium level is observed, which is still the level of the concentration in september. The latest growth rate indicates a development in the concentration of SARS-CoV-2 in wastewater corresponding to the category "No Growth". Data updated Oktober 22, 2025.

Regional concentration levels of SARS-CoV-2 in wastewater and development over time

The figure below shows the level of SARS-CoV-2 in wastewater for each region, along with the regional development of SARS-CoV-2 concentration over time.

The figure shows a map of Denmark divided into regions and colored according to the SARS-CoV-2 level in wastewater during the past week. In addition, the figure shows a graph over each region with the development of the average concentration of SARS-CoV-2 in wastewater over the past 16 months. The concentration is adjusted according to the amount of feces in the wastewater to account for dilution and changes in the number of people contributing to the wastewater. The concentration is divided into five levels (very low, low, medium, high, and very high), which are marked as horizontal bands on the figure. Peaks at medium level are observed in the winter of 2024–25, after which the concentration declines to a very low level in all regions up to July 2025, where it begins to rise again. In all five regions, the concentration is at a medium level.

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Data from the national wastewater surveillance of SARS-CoV-2 (22.10.2025)

Information on the National Wastewater Surveillance of SARS-CoV-2

How is the national wastewater surveillance of SARS-CoV-2 conducted?

Where is SARS-CoV-2 measured in wastewater?

How is SARS-CoV-2 measured in wastewater?

How are the wastewater measurement results reported?

Where can I learn more about the national wastewater surveillance?

 

Publications

Predicting hospital admissions due to COVID-19 in Denmark using wastewater-based surveillance. Gudde, A., Krogsgaard, L. W., Benedetti, G., Schierbech, S. K., Brokhattingen, N., Petrovic, K., Rasmussen, L. D., Franck, K. T., Ethelberg, S., Larsen, N. B., & Christiansen, L. E. (2025). The Science of the total environment, 966, 178674. https://doi.org/10.1016/j.scitotenv.2025.178674

A survey of the representativeness and usefulness of wastewater-based surveillance systems in 10 countries across Europe in 2023. Benedetti, G., Wulff Krogsgaard, L., Maritschnik, S., Stüger, H. P., Hutse, V., Janssens, R., Blomqvist, S., Pitkänen, T., Koutsolioutsou, A., Róka, E., Vargha, M., La Rosa, G., Suffredini, E., Cauchie, H. M., Ogorzaly, L., van der Beek, R. F., Lodder, W. J., Madslien, E. H., Baz Lomba, J. A., & Ethelberg, S. (2024). Euro surveillance: European communicable disease bulletin, 29(33), 2400096. https://doi.org/10.2807/1560-7917.ES.2024.29.33.2400096

Results from the SARS-CoV-2 wastewater-based surveillance system in Denmark, July 2021 to June 2022. Krogsgaard, L. W., Benedetti, G., Gudde, A., Richter, S. R., Rasmussen, L. D., Midgley, S. E., Qvesel, A. G., Nauta, M., Bahrenscheer, N. S., von Kappelgaard, L., McManus, O., Hansen, N. C., Pedersen, J. B., Haimes, D., Gamst, J., Nørgaard, L. S., Jørgensen, A. C. U., Ejegod, D. M., Møller, S. S., ... Ethelberg, S. (2024). Water Research, 252. https://doi.org/10.1016/j.watres.2024.121223

Detection of Sequencing Reads from 5’-End Genomic and Subgenomic SARS-CoV-2 RNAs in Wastewater Sampled, Extracted and Sequenced Directly from Aircrafts, Airport Buildings, or Regular Wastewater Treatment Plants. Tang, M.-H. E., Bennedbaek, M., Gunalan, V., Qvesel, A. G., Thorsen, T. H., Rasmussen, L. D., Krogsgaard, L. W., Rasmussen, M., Stegger, M., & Alexandersen, S. (2023). Heylion 2024, May 15. https://doi.org/10.1016%2Fj.heliyon.2024.e29703

Early detection of local SARS-CoV-2 outbreaks by wastewater surveillance: A feasibility study. Nauta, M., McManus, O., Træholt Franck, K., Lindberg Marving, E., Dam Rasmussen, L., Raith Richter, S., Ethelberg, S. (2023) Epidemiology & Infection, 151, e28. https://doi.org/10.1017/S0950268823000146

First cases of SARS-CoV-2 BA.2.86 in Denmark, 2023. Rasmussen, M., Møller, F. T., Gunalan, V., Baig, S., Bennedbæk, M., Christiansen, L. E., Cohen, A. S., Ellegaard, K., Fomsgaard, A., Franck, K. T., Larsen, N. B., Larsen, T. G., Lassaunière, R., Polacek, C., Qvesel, A. G., Sieber, R. N., Rasmussen, L. D., Stegger, M., Spiess, K., Tang, M. E., … Jokelainen, P. (2023). Euro surveillance: European communicable disease bulletin, 28(36), 2300460. https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2023.28.36.2300460

Wastewater Surveillance in Europe for Non-Polio Enteroviruses and Beyond. Bubba, L., Benschop, K. S. M., Blomqvist, S., Duizer, E., Martin, J., Shaw, A. G., Bailly, J. L., Rasmussen, L. D., Baicus, A., Fischer, T. K., & Harvala, H. (2023). Microorganisms, 11(10), 2496. https://doi.org/10.3390/microorganisms11102496

SARS-CoV-2 Variants BQ.1 and XBB.1.5 in Wastewater of Aircraft Flying from China to Denmark, 2023. Qvesel, A. G., Bennedbæk, M., Larsen, N. B., Gunalan, V., Krogsgaard, L. W., Rasmussen, M., & Rasmussen, L. D. (2023).Emerging Infectious Diseases, 29(12). https://doi.org/10.3201/eid2912.230717

Predicting COVID-19 Incidence Using Wastewater Surveillance Data, Denmark, October 2021-June 2022. McManus, O., Christiansen, L. E., Nauta, M., Krogsgaard, L. W., Bahrenscheer, N. S., von Kappelgaard, L., Christiansen, T., Hansen, M., Hansen, N. C., Kähler, J., Rasmussen, A., Richter, S. R., Rasmussen, L. D., Franck, K. T., & Ethelberg, S. (2023). Emerging Infectious Diseases, 29(8). https://doi.org/10.3201/eid2908.221634