Wastewater based surveillance SARS-CoV-2
Wastewater-based Surveillance
on
SARS-CoV-2
AMELAG - Weekly report
12.06.2024
The SARS-CoV-2 viral load in wastewater is being monitored as part of AMELAG (“Abwassermonitoring für die epidemiologische Lagebewertung”, German for wastewater monitoring for epidemiological situation assessment). Data from 163 sites, i.e. wastewater treatment plants (WWTP), are currently included in the analyses. For the calendar week 23 data from 73 sites were available. Data from other sites will be provided later.
The COVID-19 situation is assessed in the weekly report on acute respiratory diseases (ARE weekly report) in conjunction with other indicators. A comparsion 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 order to obtain an overall picture of the mean viral load and its development. To this end, 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. Figure 1 shows the course of these weekly values (grey dots), a regression curve (black line, estimated using the LOESS method) as well as the uncertainty associated with this curve, calculated as pointwise 95% confidence intervals (light blue area). The viral loads are currently low but showing a slight increase. Last week’s development may still change due to late notifications, especially due to late notifications from sites with large population coverage.
Figure 1: Aggregated SARS-CoV-2 load in wastewater over time
along with regression curve and associated 95% confidence intervals. The
data was last updated on Tuesday the 11.06.2024, 10 am. The latest data
used in the calculations is from the previous Wednesday’s sampling
(05.06.2024, CW 23). Shown are 7-day averages, which refer to the period
from Thursday to Wednesday; the most recent value is calculated from the
data from 30.05.2024 (CW 22), to 05.06.2024 (CW 23). The date of the
sample corresponds to the start date of the 24-hour composite sample.
The time
period displayed can be adjusted using the buttons on the top left. 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. It should be taken into account when
interpreting the data that 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 data from
sites for which data is available from the last five calendar weeks is
included. The number of sites included at each point in time may differ
between the figures, as the sites with fewer
than 10 data points are not included in all figures.
Data for
further sites will be supplied subsequently.
Additionally, the course of the viral load in wastewater is shown for the individual WWTPs in Figure 2. Displayed are the normalized viral loads measured at a WWTP (grey dots), a corresponding regression curve (black line, estimated using the LOESS method) and the uncertainty associated with the estimated curve, calculated as pointwise 95% confidence intervals (light blue area).