National wastewater surveillance of SARS-CoV-2

The national wastewater surveillance 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 01.04.2026

In week 13 (March 23 - March 29) the national SARS-CoV-2 concentration in wastewater, indicating the amount of SARS-CoV-2 circulating in the population, is at a very low level.

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

The national growth rate, which is the average weekly growth over the past four weeks (March 2 - March 29), is not calculated this week due to increased uncertainty caused by very low concentrations.

 

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 growth rate is categorized as follows:

  • Very strong increase (> 50%)
  • Strong increase (25% to 49%)
  • Increase (10% to 24%)
  • No growth (-9% to 9%)
  • Decrease (-24% to -10%)
  • Strong decrease (-49% to -25%)
  • Very strong decrease (< -50%)

Linegraph showing the development of the average weekly concentration of SARS-CoV-2 in wastewater over the past 11 months, from March 2025 to February 2026. The line represents the virus concentrationon on log scale, adjusted according to the amount of feces in the wastewater, and is divided into five levels (very low, low, medium, high, and very high), which are marked as horizontal bands on the figure. The graphs shows a decrease from low level to very low level March 2025. The concentration then lies at this level until June, followed by an increase from very low level to medium level, June to August. The concentration then lies at this level until February, followed by a decrease from medium level to very low level, within the same month. Data updated april 1.

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, and fluctuates around a medium level. The concentration peaks around the end of December, after which it decreases.

 

Download wastewater data

Data from the national wastewater surveillance (01.04.2026)




Information on the National Wastewater Surveillance

How is the national wastewater surveillance conducted?

Where are viruses measured in wastewater?

How are viruses measured in wastewater?

How are the wastewater measurement results reported?

Where can I learn more about the national wastewater surveillance?

Publications

Exploring bilateral collaboration for enhanced pandemic preparedness: A pilot study on joint wastewater surveillance in Denmark and Norway. Madslien, E. H., Krogsgaard, L. W., Gudde, A., Petrovic, K., Larsen, N. B., Shaw, D. S., Benedetti, G., & Hyllestad, S. (2026). Science of the Total Environment, 1027, 181654. https://doi.org/10.1016/j.scitotenv.2026.181654

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). 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