Coronavirus (COVID-19): SARS-CoV-2 in wastewater and persons tested positive for SARS-CoV-2

FigureThe dataset shows the 7-day median of the RNA copies of the specified virus per day and 100’000 persons in the wastewater of the wastewater treatment plant (ARA) Basel as well as the 7-day median of the corresponding case numbers. The dataset is usually updated on Tuesdays with the data up to the previous Sunday. The ProRheno AG (operator of the ARA Basel) takes a 24-hour sample of the raw wastewater, which is examined by the Cantonal Laboratory Basel-Stadt (KL BS) for RNA of the specified viruses. The measurement methodology has not been changed since the start of the monitoring: see publication [https://smw.ch/index.php/smw/article/view/3226](https://smw.ch/index.php/smw/article/view/3226). The plausibility of the values is continuously checked on the basis of internal quality parameters. The study area includes the catchment area of the ARA Basel, which consists mainly of the canton of Basel-Stadt as well as the municipalities of Allschwil, Binningen, Birsfelden, Bottmingen, Oberwil and Schönenbuch (all cantons of Baselland). Until the end of June 2023, the KL CB’s measured values were also presented on the wastewater dashboard of the FOPH [Covid-19 Switzerland | Coronavirus | Dashboard (https://www.covid19.admin.ch/en/epidemiologic/waste-water?wasteWaterFacility=270101)](https://www.covid19.admin.ch/en/epidemiologic/waste-water?wasteWaterFacility=270101). As of July 2023, the measured values of EAWAG [SARS-CoV2 in wastewater - Eawag](https://www.eawag.ch/de/abteilung/sww/projekte/sars-cov2-im-abwasser/) ([https://www.eawag.ch/de/abteilung/sww/projekte/sars-cov2-im-abwasser/](https://www.eawag.ch/de/abteilung/sww/projekte/sars-cov2-im-abwasser/) are published on this page, which also examines the raw wastewater of ARA Basel. The investigation methods used by KL BS and EAWAG are very similar but not identical. For this reason, there may be deviations. The measurements are continued independently of the EAWAG by the KL BS in order to obtain more timely measured values, with additional standardization factors and the flexibility to integrate further analytes. The values originally presented from 22.03. to 01.10.2023 had to be corrected downwards due to an incorrect setting in the measurement software, which has an influence on the RNA quantification, and are now displayed correctly.Case numbersThe case numbers correspond to the number of confirmed and reported cases of the infections presented to the canton in the catchment area of the ARA Basel.Interpretation of the curvesThe monitoring of viruses in wastewater is primarily about detecting trends (in particular, of course, the increase of a circulating virus). It is not possible to derive a certain number of cases or the severity of an infection. A comparison of the curve rash (height of the peaks) at different times is hardly possible, because e.g. different virus variants lead to different virus amounts per case. Different virus variants can also affect the symptoms, so that e.g. infections in humans run without a trace, but still viruses are released into the wastewater.