This project is led by associate professor Zeynep Cetecioglu Gurol and supported by Mariel Perez-Zabaleta and Isaac Owusu-Agyeman at KTH Royal Institute of Technology (KTH). Bioinformatics analyses of wastewater samples are led by assistant professor Luisa Hugerth (Uppsala University). This group of researchers is known as SEEC-KTH. The project was established as a collaboration with the SEED and Chemical Engineering departments at KTH. The project is now funded as part of the SciLifeLab Pandemic Laboratory Preparedness Program. SEEC-KTH is now part of the Department of Industrial Biotechnology at KTH.

The data and visualisations on this page are no longer being updated. This dashboard combines data from two periods:

• Recent period (September 2021–June 2023): Data collected using the Promega kit for concentration, starting from week 35 of 2021.
• Historic period (April 2020–August 2021): Data collected using the initial concentration method based on earlier studies.

Wastewater collection sites

The analysis of wastewater samples from Stockholm by SEEC-KTH was conducted in close collaboration with Stockholm Vatten och Avfall and the Käppala Association. Sampling began in mid-April 2020 at the Bromma, Henriksdal, and Käppala wastewater treatment plants. These plants receive wastewater from populations of approximately 360,000, 860,000, and 500,000 people, respectively. Consult the catchment maps for Käppala and Bromma and Henriksdal.

SEEC-KTH began collecting wastewater samples from the Sjölunda wastewater treatment plant in Malmö in week 39 of 2021. This plant services most of Malmö, Burlöv municipality, and parts of Lomma, Staffanstorp, and Svedala. Around 300,000 people live in its catchment area. Download information about the Sjölunda catchment area.

Overall, SEEC-KTH analysed wastewater from around 20% of Sweden's population.

Recent data (September 2021–June 2023)

This section displays data from September 2021 onwards, when the concentration method changed to use the Promega kit. Data collection ceased in June 2023.

Recent methods

Starting in week 35 of 2021, the group used the Promega kit for concentration. To correct for variations in population size and wastewater flow, the group quantified pepper mild mottle virus (PMMoV) using a modified version of the assay by 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). SARS-like virus-specific N3 primers (Lu et al., 2020) with SYBR Green chemistry (Perez-Zabaleta et al., 2023) were used to quantify SARS-CoV-2.

Visualisations

The recent visualisations show the latest 16 weeks by default. Use the Whole timeline button in each plot to display all available data. Differences in wastewater collection systems and populations may bias direct comparisons between cities.

Using the interactive plots

Double-click a site in the legend to show only that site, or single-click it to toggle the site. Use the plot buttons to deselect or reselect all areas and to switch between the recent period and the whole timeline. Drag within a plot to zoom into an axis range, hover over a point to read its value, and use the Plotly toolbar to zoom, autoscale, or reset the axes.

Stockholm

Malmö

Recent dataset

The recent Stockholm and Malmö data can be downloaded using the link beneath either recent visualisation. Results are available partially from week 16 of 2020 for Stockholm and from week 39 of 2021 for Malmö, with the final measurements in week 22 of 2023.

Contact: zeynepcg@kth.se

How to cite the dataset

Cetecioglu, Z. G., Williams, C., Khatami, K., Atasoy, M., Nandy, P., Jafferali, M. H., and Birgersson, M. (2021). SARS-CoV-2 Wastewater Data from Stockholm, Sweden. https://doi.org/10.17044/scilifelab.14315483.

Historic data (April 2020–August 2021)

This section displays the amount of SARS-CoV-2 in Stockholm wastewater between April 2020 and August 2021. The amount was calculated as gene copies per week in raw wastewater with bovine and PMMoV factors. The method changed from September 2021 onwards.

Historic methods

After concentration, filtering, and preparation, samples were analysed using qPCR for SARS-CoV-2 RNA. Primers targeting the nucleocapsid gene, previously used and verified by Medema et al. (2020), were used to detect SARS-CoV-2. Some raw wastewater samples were frozen at −20°C, while concentrated wastewater or purified RNA was stored at −80°C before the next analysis step.

The concentration method was based on the study by Jafferali et al. (2021), which compared four concentration methods and found the KTH double-ultrafiltration method significantly more efficient than single-filtration and adsorption methods.

Historic visualisation — Stockholm

All samples up to week 21 of 2020 were received by the laboratory in week 21. Between weeks 21 and 33 of 2020, samples were analysed every two weeks. After week 33, samples were usually analysed weekly, except between weeks 24 and 32 of 2021, when measurements were taken every two weeks.

Historic dataset

The historic Stockholm dataset is available from the SciLifeLab Data Repository: SARS-CoV-2 Wastewater Data from Stockholm, Sweden. It contains Stockholm totals and data for the Henriksdal, Sickla, Hässelby, Järva, Riksby, and Käppala inlets. At least partial data are available from week 16 of 2020 through week 34 of 2021.

Methods

This dashboard combines periods with different methodologies. In September 2021, starting in week 35, the group changed to the Promega concentration kit.

Recent methods (September 2021–June 2023)

The group quantified PMMoV to correct for population size and wastewater flow. SARS-like virus-specific N3 primers with SYBR Green chemistry were used to quantify SARS-CoV-2. After concentration, filtering, and preparation, samples were analysed using qPCR for SARS-CoV-2 RNA.

Historic methods (April 2020–August 2021)

The initial method used double ultrafiltration and nucleocapsid-gene primers. For details, see Jafferali et al. (2021).

Related data

The KTH group analysed SARS-CoV-2 variants in Stockholm and Malmö wastewater during 2021–2022. The sequence data are available from the European Nucleotide Archive under project PRJEB60156.