COVID-⁠19 Switzerland

Information on the current situation, as of 23 May 2023

The key figures will be published each Tuesday at 15:30.

Epidemiological course,Appenzell Ausserrhoden

Viral load in wastewater

The data published here are based on information obtained from the federal government's national wastewater monitoring system. Since January 2022, the national wastewater monitoring system of Switzerland and the Principality of Liechtenstein has determined the SARS-⁠CoV-⁠2 viral load in the wastewater of participating wastewater treatment plants (WWTP) at regular intervals.

Wastewater samples are collected from wastewater treatment plants three to six times per week. The absolute viral load (gene copies/day) is specified per 100,000 inhabitants. A dilution factor based on the wastewater treatment plant's flow volume is taken into account, for instance during dry periods. The relative viral load is the measured viral load (gene copies/day) as a proportion of the historically measured maximum value. The proportion of relative viral load is calculated by dividing the proportion of absolute viral load by the proportion of the historic maximum viral load value. The residential population comprises the catchment area of each wastewater treatment plant (WWTP). Seasonal fluctuations in the non-⁠permanent population, which influence the viral load particularly in busy tourist areas, are not included. Wastewater treatment plants (WWTP) no longer participating in the project will not be included when calculating the proportion of viral load per category. However, historical measurements will still be available when viewing the development over time.

Detailed information on the measuring methods and terminology can be found on the Eawag website. New findings may prompt adjustments to data calculations. In certain cases, modifications to the sampling process and/or lab methodologies reduce comparability with data previously obtained. This concerns the wastewater treatment facilities in Burgdorf (whose sampling scheme was modified with effect from 23 August 2022) as well as Aarau, Aarburg, Appenzell (Boedeli), Baden, Bremgarten, Brugg, Hallau (Klettau), Kaisten, Lenzburg, Neuhausen am Rheinfall (Roeti), Ramsen (Bibertal-⁠Hegau), Wohlen and Zofingen (whose lab methodologies were modified with effect from 30 October 2022).

The timeframe desired can be selected using the slider below the chart.

Geographical distribution

Viral load in wastewater, Appenzell Ausserrhoden, 07.02.2022 to 22.05.2023

The graph shows the relative viral load in per cent as a 7-⁠day average in the wastewater treatment plants (WWTPs) and the difference in viral load compared with the previous week in percentage points (pp) in Switzerland and Liechtenstein. The percentage point figure is used to compare percentages. The 7-⁠day relative share refers to the historical maximum values for each wastewater treatment plant.
Canton Appenzell Ausserrhoden
Relative viral load Number of WWTPProportion of WWTP
0-⁠20% - -
20-⁠40% - -
40-⁠60% - -
60-⁠80% - -
80-⁠100% - -
Total - -

Relative viral load (7-⁠day average)

Reporting delay
Source: FOPH – Status: 23.05.2023, 08.00h
Geographic distribution over time

View the development of the virus load in wastewater at various WWTPs in Switzerland and Liechtenstein.


Development over time

The graph shows the absolute and the relative viral load in per cent as a 7-⁠⁠day average in the wastewater treatment plants (WWTPs) in Switzerland and Liechtenstein and the difference in viral load compared with the previous week’s 7-⁠day average in percentage points (pp). The 7-⁠⁠day relative share refers to the historical maximum values for each wastewater treatment plant. Vertical lines indicate changes in methodology. Shaded areas indicate data points that are below the limit of quantification (LoQ).

Data only available for individual WWTP
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