Evaluation of wastewater SARS-CoV-2 surveillance for monitoring COVID-19 trends and early warning in Sweden, 2023–2024
4 affiliations
- 1Department of Communicable Disease Control and Health Protection, Public Health Agency of Sweden, Solna, Sweden
- 2ECDC Fellowship Programme, Field Epidemiology path (EPIET), European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden
- 3Department of Public Health Analysis and Data Management, Public Health Agency of Sweden, Solna, Sweden
- 4Department of Aquatic Sciences and Assessment, Science for Life Laboratory, Swedish University of Agricultural Sciences, Uppsala, Sweden
Abstract
Wastewater surveillance (WWS) of SARS-CoV-2 RNA levels offers a way to monitor virus circulation independently of clinical testing. With COVID-19 now endemic, clarifying the role of WWS within routine surveillance is essential. The aim was to evaluate the potential of WWS as an early warning indicator for COVID-19 in Sweden, based on its correlation with reported case data. The study includes data from July 2023 to December 2024, from 19 wastewater treatment plants (WWTPs), covering 43% of Sweden’s population, and surveillance data of reported COVID-19 cases. Analyses were performed by WWTP, separately for Stockholm (4 WWTPs) and at a national level (19 WWTPs). We compared wastewater SARS-CoV-2 levels to reported COVID-19 cases using cross-correlation and prediction metrics following trend classification. Correlations and classification metrics were highest without time shifts. SARS-CoV-2 levels in wastewater were strongly correlated with reported COVID-19 cases, with median cross-correlation values of 0.80 across all WWTPs and 0.87 at Stockholm and national levels. Positive predictive values of wastewater data to reported cases ranged from 63–74%, and negative predictive values from 85–95%. Sensitivity and specificity in Stockholm reached 78% and 87%; at national level, 72% and 84%, respectively. Under the evaluated weekly sampling and reporting system, WWS did not demonstrate a consistent early-warning advantage over reported cases but may support monitoring of trends when clinical testing is reduced.
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BibTeX
@article{ohlson2026evaluation,
title = {{Evaluation of wastewater SARS-CoV-2 surveillance for monitoring COVID-19 trends and early warning in Sweden, 2023–2024}},
author = {Anna Ohlson and Moa Rehn and Sharon Kühlmann Berenzon and Erik Sturegård and Rakel Brodin and Anna J. Székely and Sofia Persson and Ilias Galanis},
journal = {PLOS One},
year = {2026},
month = sep,
doi = {10.1371/journal.pone.0358326},
url = {https://doi.org/10.1371/journal.pone.0358326},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Evaluation of wastewater SARS-CoV-2 surveillance for monitoring COVID-19 trends and early warning in Sweden, 2023–2024
AU - Anna Ohlson
AU - Moa Rehn
AU - Sharon Kühlmann Berenzon
AU - Erik Sturegård
AU - Rakel Brodin
AU - Anna J. Székely
AU - Sofia Persson
AU - Ilias Galanis
PY - 2026
DA - 2026/09/21
JO - PLOS One
DO - 10.1371/journal.pone.0358326
UR - https://doi.org/10.1371/journal.pone.0358326
AB - Wastewater surveillance (WWS) of SARS-CoV-2 RNA levels offers a way to monitor virus circulation independently of clinical testing. With COVID-19 now endemic, clarifying the role of WWS within routine surveillance is essential. The aim was to evaluate the potential of WWS as an early warning indicator for COVID-19 in Sweden, based on its correlation with reported case data. The study includes data from July 2023 to December 2024, from 19 wastewater treatment plants (WWTPs), covering 43% of Sweden’s population, and surveillance data of reported COVID-19 cases. Analyses were performed by WWTP, separately for Stockholm (4 WWTPs) and at a national level (19 WWTPs). We compared wastewater SARS-CoV-2 levels to reported COVID-19 cases using cross-correlation and prediction metrics following trend classification. Correlations and classification metrics were highest without time shifts. SARS-CoV-2 levels in wastewater were strongly correlated with reported COVID-19 cases, with median cross-correlation values of 0.80 across all WWTPs and 0.87 at Stockholm and national levels. Positive predictive values of wastewater data to reported cases ranged from 63–74%, and negative predictive values from 85–95%. Sensitivity and specificity in Stockholm reached 78% and 87%; at national level, 72% and 84%, respectively. Under the evaluated weekly sampling and reporting system, WWS did not demonstrate a consistent early-warning advantage over reported cases but may support monitoring of trends when clinical testing is reduced.
SN - 1932-6203
ER -