Wastewater Surveillance

The SARS-CoV-2 and influenza viral load in wastewater is being tested at selected wastewater treatment plants (WWTP) in Germany as part of AMELAG (“Abwassermonitoring für die epidemiologische Lagebewertung”, German for wastewater monitoring for epidemiological situation assessment). Data from 169 WWTPs are currently included in the analyses. For the calendar week 50 data from 135 WWTPs were available. Data from other WWTPs are provided continuously.

An assessment of the overall situation is conducted in conjunction with other indicators in the weekly report on acute respiratory diseases (ARE weekly report). A comparison between the aggregated SARS-CoV-2 viral load in wastewater and the COVID-19 incidence is shown in the weekly Grippeweb report.

The course of the viral loads aggregated across all sites is shown in Figure 1 in order to obtain an overall picture of the mean viral load and its development in Germany. Weekly mean values of the viral loads (given in gene copies / liter), previously transformed by the common logarithm, are computed, first for each site and then across all sites for the respective week. The mean values are weighted according to the number of inhabitants connected to the respective site. The estimation of the regression curve is also weighted, so that weekly mean values with higher uncertainty are given a lower weight in the estimation and vice versa. Currently, no clear trend can be observed in the aggregated viral load. The development observed over the last few weeks may still change due to late notifications, especially from WWTPs with large population coverage.

Figure 1: Aggregated SARS-CoV-2 load in wastewater over time (grey dots) along with a regression curve (black line, estimated using the LOESS method) and associated 95% confidence intervals (light blue area). The data was last updated on Tuesday the 17.12.2024, 10 am. The latest data used in the calculations is from the previous Wednesday’s sampling (11.12.2024, CW 50). Shown are 7-day averages, which refer to the period from Thursday to Wednesday; the most recent value is calculated from the data from 05.12.2024 (CW 49), to 11.12.2024 (CW 50). The date of the sample corresponds to the start date of the 24-hour composite sample.
The button on the right allows the display of the data points, regression curve and confidence intervals on the logarithmic scale or transformed back to the original scale. Changes in viral loads in the low value range are emphasized more strongly than values in the high value range on a logarithmic scale. By hovering over the individual points the calendar week, the date of the corresponding Wednesday, the viral load, the number of sites and the proportion of the total population that is included in the calculation at that time are shown.
Data for further sites are supplied subsequently.

The course of the viral load in wastewater is shown for the individual WWTPs in Figure 2.

Standort:

Figure 2: SARS-CoV-2 load in wastewater over time (grey dots) along with the regression curve (black line, estimated using the LOESS method) and associated 95% confidence intervals (light blue area). The individual measurements represent the average of the measured gene regions. If at least half of the measured gene regions are below the limit of quantification (LOQ), the measurement is considered as “< LOQ” (white dots). The data was last updated on 17.12.2024, 10 am. The date of the sample corresponds to the start date of the 24-hour composite sample.
The location can be selected using the filter. The button on the right allows you to display the data points, regression curve and confidence intervals on the logarithmic scale or transformed back to the original scale. Changes in viral loads in the low value range are emphasized more strongly than values in the high value range on a logarithmic scale. By hovering over the individual points the calendar week, date of sampling and viral load are shown.
Only those sites for which data are available for the last five calendar weeks are shown.
Changes in laboratory or changes in the methods used in laboratories are indicated with a dashed, vertical line.
If fewer than 10 data points are available in total, before a minimum 4-week time window with no data or before or after a change of laboratory, only the individual data points are shown. The corresponding regression curves and confidence intervals will be calculated when at least 10 data points are available.
Data from other sites are supplied subsequently.

Trends of the viral load in the wastewater can be calculated for each WWTP from the regression curves in Figure 2. These trends are shown in Figure 3. For the calendar week 50 a trend could be calculated for 98 sites. For 3 sites, the trend indicates an increasing viral load.

Figure 3: Change in SARS-CoV-2 load in wastewater per WWTP
Trend categories: “increasing” (defined as an increase of more than 15% compared to the previous week), “unchanged” (change between -15% and 15% compared to the previous week) and “decreasing” (decrease of more than 15% compared to the previous week).
The WWTP are ordered alphabetically by federal state and sorted alphabetically by WWTP within each state. The data were last updated on 17.12.2024, 10 am. The most recent data included in the trends calculated here are from the previous Wednesday’s sampling (11.12.2024, CW 50). The date of the sample corresponds to the start date of the 24-hour composite sample. As the trend is calculated as the change in the (smoothed) viral load compared to the previous week’s value, the calendar week 50 describes the period from Wednesday, the 04.12.2024 (CW 49), to Wednesday, the 11.12.2024 (CW 50). The diagram shows treatment plants for which sufficient data points were available to calculate a trend.
Changes in laboratory or changes in the methods used in laboratories are indicated with a dashed, vertical line.
Data for other sites will be supplied subsequently.

The geographical locations, along with the most recent trend of those WWTPs that have already delivered data are shown in Figure 4.

Figure 4: Map of the WWTPs showing the trend of the viral load per site.

The following WWTPs already provide data and will be included in all calculations as soon as at least 10 data points are available: Berchtesgaden, Bielefeld, Erlangen, Halberstadt, Schönebeck und Stadtbergen .

In AMELAG, wastewater samples from 8 WWTPs / sampling sites are sequenced and analyzed by the Technical University of Darmstadt as cooperation partner. This allows the relative increase or decrease (frequency in %) of already known variants to be determined (Figure 5).

According to the WHO classification, the SARS-CoV-2 variant JN.1 are currently considered as variants of interest (VOIs) and the variants KP.2, KP.3, KP.3.1.1, JN.1.18, LB.1 and XEC are considered as variants under monitoring (VUMs). All current VUMs are derived from JN.1. The variants BA.2.86 and JN.1.7 are not classified as VOI/VUM by the WHO any more.

The newest variant classified as a VUM, XEC, has been detected at the sampled sites since calendar week 36 and has been increasing since then at most of the sampling sites.

Figure 5: Percentage of current SARS-CoV-2 variants of interest (VOI) and SARS-CoV-2 variants under observation (VUM). The percentages also include all respective sublines of a variant, with the exception of the sublines specifically listed here. The results of the sampling of 8 WWTPs / sampling sites are shown since calendar week 36 2023, as far as the data are available. The selection of the sublines shown is based on the WHO classification. Further explanations of the classification can be found on the integrated genomic surveillance page. The analysis is based on the Freyja bioinformatics tool and is therefore dependent on the Freyja reference used to identify SARS-CoV-2 variants.

The SARS-CoV-2 and influenza viral load in wastewater is being tested at selected wastewater treatment plants (WWTP) in Germany as part of AMELAG (“Abwassermonitoring für die epidemiologische Lagebewertung”, German for wastewater monitoring for epidemiological situation assessment). Data from 113 WWTPs are currently included in the analyses. For the calendar week 50 influenza virus A and B data from 80 WWTPs were available. Retrospective data for the 2023/24 season as well as new data for current measurements are still being integrated into the report and will be available soon.

An assessment of the overall situation is conducted in conjunction with other indicators in the weekly report on acute respiratory diseases (ARE weekly report).

The course of the viral loads for influenza A and B virus, aggregated across all sites is shown in Figure 1 in order to obtain an overall picture of the mean viral load and its development in Germany. Weekly mean values of the viral loads (given in gene copies / liter), previously transformed by the common logarithm, are computed, first for each site and then across all sites for the respective week. The estimation of the regression curve is weighted, so that weekly mean values with higher uncertainty are given a lower weight in the estimation and vice versa. The values for influenza A and B viruses are currently in the low range, but exhibit a steadily increasing trend within the last weeks.

Figure 1: Aggregated viral loads for influenza A and influenza B viruses in wastewater over time along with regression curve (estimated using the LOESS method) and associated 95% confidence intervals. The data was last updated on Tuesday the 17.12.2024, 10 am. The latest data used in the calculations is from the previous Wednesday’s sampling (11.12.2024, CW 50). Shown are 7-day averages, which refer to the period from Thursday to Wednesday; the most recent value is calculated from the data from 05.12.2024 (CW 49), to 11.12.2024 (CW 50). The date of the sample corresponds to the start date of the 24-hour composite sample.
The button on the right allows the display of the data points, regression curve and confidence intervals on the logarithmic scale or transformed back to the original scale. Changes in viral loads in the low value range are emphasized more strongly than values in the high value range on a logarithmic scale. By hovering over the individual points the calendar week, the date of the corresponding Wednesday, the viral load, the number of sites and the proportion of the total population that is included in the calculation at that time are shown.
Only those sites for which data are available for the last five calendar weeks are included here.
Data for further sites are supplied subsequently.

The course of the viral load in wastewater is shown for the individual WWTPs in Figure 2.

Standort:

Figure 2: Viral loads for influenza A and influenza B viruses in wastewater over time (green and yellow points, respectively) along with the regression curves (green and yellow lines, estimated using the LOESS method, respectively) and corresponding 95% confidence intervals (light green and light yellow shaded areas). Measurements below the limit of quantification are shown as white points. The data was last updated on 17.12.2024, 10 am. The date of the sample corresponds to the start date of the 24-hour composite sample.
The location can be selected using the filter. The button on the right allows the display of the data points, regression curve and confidence intervals on the logarithmic scale or transformed back to the original scale. Changes in viral loads in the low value range are easier to recognize on a logarithmic scale. By hovering over the individual points the calendar week, date of sampling and viral load are shown.
If fewer than 10 data points are available in total, before a minimum 4-week time window with no data or before or after a change of laboratory, only the individual data points are shown. The corresponding regression curves and confidence intervals will be calculated when at least 10 data points are available.
Data from other sites are supplied subsequently.

Figure 3 shows the proportions of samples for influenza A and B viruses that are above or below the limit of quantification (LOQ). Typically, two samples are taken weekly at each WWTP. Overall, most of the measured values are below the limit of quantification.

Influenza A virus

Influenza B virus

Figure 3: Proportion of influenza A and B virus samples with measured viral loads above or below the LOQ. The numbers within the bars show the samples collected in the respective categories for the corresponding calendar week.

The geographic locations of the WWTP where influenza virus particles are detected in wastewater are shown in Figure 4.

Figure 4: Map of the WWTPs currently testing influenza viruses in wastewater.

For some infectious diseases, infected individuals excrete pathogens through fecal matter. Specialized laboratories can process wastewater samples and detect these pathogens. This enables the monitoring of the infection dynamics in the population served by the respective WWTP.

In AMELAG, SARS-CoV-2 and influenza viruses are monitored in wastewater. Nationwide, 168 WWTP are participating. The German Environment Agency (UBA) and the Robert Koch Institute (RKI) are collaborating with the Bundeswehr Medical Service, state health and environmental authorities, laboratories, universities, and the operators of WWTPs. The project is funded by the Federal Ministry of Health (BMG).

The SARS-CoV-2 data presented in the report originate from the projects AMELAG, ESI-CorA, COVIDready, Sars-GenASeq, Abwasser Biomarker CoV-2, and state-funded projects. ESI-CorA was funded by the European Commission under the Emergency Support Instrument (No 060701/2021/864650/SUB/ENV.C2). COVIDready, Sars-GenASeq and Abwasser Biomarker CoV-2 were funded by the Federal Ministry of Education and Research (BMBF).

The methods for sampling, analytics, logistics, and data transmission and processing are described in four technical guidelines on http://www.rki.de/abwassersurveillance.

The data and software code of AMELAG are published on Zenodo and GitHub.

The exact procedures and potential use cases for wastewater surveillance are described in Epidemiological Bulletin 34/2024.

Limitations

Wastewater data do not allow conclusions to be drawn about disease severity or the burden on the healthcare system. Based on current knowledge, wastewater data cannot precisely determine incidence/prevalence or underreporting. For epidemiological assessments, wastewater data should always be considered in combination with other indicators, e.g. from syndromic surveillance.

Absolute viral loads cannot be directly compared to the number of infected individuals, especially over longer time periods, as the viral load excreted per infected person may vary, for example, between different virus variants. Likewise, absolute viral loads should not be compared between different sites and pathogens due to differences in sampling, laboratory techniques, normalization, and pathogen-specific differences.

The values obtained are influenced by a variety of factors (e.g., changes in wastewater inflow, heavy rainfall events, or tourist activities), which can only be partially compensated for through normalization of the data.

Suggested citation
Robert Koch-Institut, Umweltbundesamt: AMELAG-Weekly Report CW 51/2024 | DOI: 10.25646/12960

Wastewater Surveillance

Wastewater Surveillance

AMELAG Weekly Report 18.12.2024

Influenza A virus

Influenza B virus

AMELAG Weekly Report
18.12.2024