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.

Updated 17 September 2025

SARS-CoV-2 status in wastewater as of 17.09.2025

In week 37 (September 8 - September 14) 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 Capital Region of Denmark the concentration is at a low level and in Central Denmark Region, North Denmark Region, Region Zealand and Region of Southern Denmark the concentration is at a medium level.

The national growth rate, which is the average weekly growth over the past three weeks (August 25 - September 14), shows a development in the SARS-CoV-2 wastewater concentration corresponding to the category "Strong increase".

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.

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.

Download wastewater data

Data from the national wastewater surveillance of SARS-CoV-2 (17.09.2025)

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?

Particles of the SARS-CoV-2 virus are shed in the feces of approximately 50 % of infected individuals and can therefore be detected in wastewater.
Wastewater samples are collected using an automatic sampler over a 24-hour period. Personnel at treatment plants collect the samples and record relevant data associated with the sampling.
The wastewater samples are transported to the Statens Serum Institut (SSI), Department of Virology and Microbiological Special Diagnostics, where they are pre-processed and analyzed using real-time quantitative polymerase chain reaction (RT-qPCR) to estimate the number of SARS-CoV-2 virus particles per liter of wastewater.
The naturally occurring plant virus Pepper Mild Mottle Virus (PMMoV), which is ingested through food and excreted in feces, is used as an indirect measure of the amount of fecal matter in wastewater. By measuring the concentration of PMMoV, adjustments can be made for wastewater dilution (e.g., due to rainwater) and the number of people using the sewage system in each catchment area.
The laboratory results are analyzed by the Department of Infectious Disease Epidemiology at SSI.

How are the wastewater measurement results reported?

The wastewater results are compiled weekly as:

A weekly weighted average concentration of SARS-CoV-2 in wastewater, which is categorized in one of five levels, ranging from very low to very high concentration. This is done for each region and for the entire country.
A growth rate that describes the change in the national concentration level based on the past three weeks of data. The growth rate is, however, not calculated or published if the SARS-CoV-2 concentration is at a very low level or if sample testing is associated with high uncertainty due to significant dilution.

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