Historic SARS-CoV-2 wastewater data (SEEC-SLU)

The data presented on this page was generated in the SLU (Swedish University of Agricultural Sciences) laboratories of SEEC (Swedish Environmental Epidemiology Center). The project was part of SciLifeLab's Pandemic Laboratory Preparedness (PLP) Program , led by Anna J. Székely (Department of Aquatic Sciences and Assessment, SLU). Wastewater analyses were overseen by Anna J. Székely and Maja Malmberg (Virology Unit of the Department of Biomedical Science and Veterinary Public Health, SLU). This page describes the historic quantification of SARS-CoV-2 levels in wastewater across multiple Swedish cities. The project achieved the broadest geographic coverage across Sweden, covering data for approximately 43% of the Swedish population.

Please note that the data and visualisations on this page are historic snapshots. The scores in the datasets and plots below are final, although minor corrections may have been applied retrospectively. This dashboard serves as a record of the project’s results during the active monitoring period.

Wastewater collection sites

SLU-SEEC collected and analysed samples from multiple wastewater treatment plants (WWTP). The table below summarises the monitored towns/cities, associated WWTPs, estimated population sizes for each catchment, and the start and end dates for monitoring. Values marked with an asterisk (\*) indicate BOD-7 estimates rather than the exact number of connected residents. A copy of the table is also available as an Excel download .

Visualisations

Important note: Historical data for Ekerö, Enköping, Knivsta, Tierp, Vaxholm, Älvkarleby, and Österåker remain available in the dataset but are not displayed in the plot below.

While identical laboratory methods were used across sites, differences in wastewater collection systems and population sizes can bias direct comparisons between localities.

How to use the interactive features of the plot

View data from particular sites: Double-click a site name in the legend to focus on a single site. Single-click to toggle a site on or off. Use the “Deselect all areas”/“Reselect all areas” buttons to quickly adjust the selection.

Adjust axis ranges: Click and drag to define a rectangle across the axes to zoom in on a specific time window or value range.

Inspect exact values: Hover over a data point to show a tooltip with the precise values for all sites on that date.

Additional plot controls: Use the toolbar in the top-right corner of the plot to zoom, autoscale, or reset the axes.

Code used to produce plot: Script to produce plot.

Commentary from the research group

Reports from the research group

Summaries of the latest findings are available as downloadable reports. The most recent version (in Swedish) can be accessed here.

Dataset

Methods

For most cities, raw untreated wastewater samples that represent a single day are collected using flow-compensated samplers at the WWTP. Uppsala is the exception: since week 16 of 2021, daily samples have been combined flow-proportionally into one composite weekly sample for the purpose of analyses.

Collected samples are processed according to standard methodologies. For samples collected up to and including week 18 of 2021, viral particles were concentrated using the electronegative filtration method (Ahmed et al., 2020). From week 19 of 2021 onwards, viral genomic material has been concentrated and extracted via the direct capture method using the Maxwell RSC Enviro TNA kit (Promega).

Absolute quantification of SARS-CoV-2 copy numbers is performed using One-Step RT-qPCR. Until week 31 of 2023, quantification of the viral genomes was performed using the SARS-CoV-2 specific N1 assay from the Centers for Disease Control and Prevention (CDC). From week 32 of 2023, the Flu SC2 Multiplex Assay (CDC) has been applied. To correct for variations in population size and wastewater flow, the pepper mild mottle virus (PMMoV) is quantified via a modified version of the assay of Zhang et al. (2006). PMMoV is an abundant RNA virus in human faeces and serves as an estimator of human faecal content (Symonds et al., 2019). Further details on the processing workflow and an evaluation of the PMMoV normalisation approach in Sweden can be found in Isaksson et al. (2022).

The graphs and dataset represent the ratio of the copy numbers measured by the Flu SC2 Multiplex Assay and PMMoV-assays, multiplied by 1000. As the Flu SC2 Multiplex Assay provides a proxy for SARS-CoV-2 virus content in the wastewater and PMMoV is a proxy of the faecal content (which is related to the contributing population), the ratio of the two can be considered to be a proxy for the prevalence of COVID-19 infections in the population of the wastewater catchment area. To align the data generated by the current method with the data generated by methods and quantification assays used earlier, older data has been transformed using conversion factors. The conversion factors are estimated based on common alignment periods when old and new methods are used in parallel.

Historic wastewater data for Umeå and Örebro

This page displays data on the amount of SARS-CoV-2 in Umeå and Örebro wastewater between October 2020 and June 2021. A new method was used after June 2021, and the most recent data can be found here.

The data displayed here were collected as part of a research project led by associate professor Maja Malmberg (SLU, Swedish University of Agricultural Sciences: maja.malmberg@slu.se), in collaboration with the SciLifeLab COVID-19 National Research Program, and associate professor Mette Myrmel at the Norwegian University of Life Sciences.

Samples of wastewater were taken from the wastewater treatment facilities in Umeå and Örebro to determine the amount of SARS-CoV-2 in wastewater. Consult the catchment area maps for Umeå and Örebro to see where the wastewater came from in each case. To determine the levels of SARS-CoV-2 in wastewater samples, ultrafiltration and qPCR were used after sample preparation. Primers previously used and verified by Corman et al. (2020) were used to detect SARS-CoV-2, and qPCR samples were normalised against the levels of pepper mild mottle virus (PMMV). Up until January 2021, three samples of wastewater were taken from each wastewater facility each week, and the results were pooled to provide a weekly estimate. After January 2021, samples were instead collected weekly.

In the plots below, the amount of SARS-CoV-2 for each week is shown relative to the amount of SARS-CoV-2 on 6th November 2020.

Amount of SARS-CoV-2 in Umeå wastewater (Oct 2020 – Jun 2021)

Download the data: Gene copy number change (%) relative to 6th Nov 2020 and flow level at each measurement, Excel file . Data are available from week 44 of 2020 until week 22 of 2021.

How to cite: Malmberg, M., Myrmel, M. & Khatri, M. (2021). Dataset of SARS-CoV-2 in wastewater in Umeå, Sweden. https://doi.org/10.17044/scilifelab.14376881.v1.

*Data for these weeks is not available.
**Samples were stored at +4 °C for 2-3 weeks, unlike all other samples.

Code used to produce plot: Script to produce plot.

Amount of SARS-CoV-2 in Örebro wastewater (Oct 2020 – Jun 2021)

Download the data: Gene copy number change (%) relative to 6th Nov 2020 and flow level at each measurement, Excel file . Data are available from week 44 of 2020 until week 22 of 2021.

How to cite: Malmberg, M., Myrmel, M. & Khatri, M. (2021). Dataset of SARS CoV-2 in wastewater in Örebro, Sweden. https://doi.org/10.17044/scilifelab.14377097.v1.

*Data for these weeks is not available.
**Samples were stored at +4 °C for 2-3 weeks, unlike all other samples.

Code used to produce plot: Script to produce plot.