There are over 300 sewage treatment plants in the Netherlands, which treat sewage that comes in from their respective catchment areas. The National Institute for Public Health and the Environment (RIVM) receives several samples of untreated sewage from all treatment plants per week. These samples are analysed for coronavirus particles in the lab of RIVM’s National Sewage Surveillance (NRS) programme.  This webpage presents the data on a map with a current overview of the measurements.

The map below will be updated using new sewage measurement data on Friday, 10 May. 

The map shows the most recent measurement for the catchment area of each sewage treatment plant, as long as it was not sampled more than 14 days ago, counting from the most recent measurement of all locations. The map is updated on the days the open dataset is published (three days per week). The data shown in this map can be found in RIVM’s open database

The number of virus particles per 100,000 residents is measured for each sewage treatment plant (STP). The different shades of blue indicate the height of the outcome of the measurements. If no virus particles were detected in the most recent measurement for a location, then that location will be coloured yellow. STPs are grey if no (validated) measurement has been performed for more than 14 days. This could be due to maintenance work on the treatment plant, for instance. Measurements for the STPs in Woerden and Katwoude are not shown, as they turned out not to be representative for the spread of the virus in these catchment areas. RIVM is still investigating the cause.

Coronavirus monitoring in sewage at Schiphol Airport

In the context of coronavirus monitoring, RIVM has been testing sewage samples taken at Schiphol Airport since 17 February 2020. At this point, 4 sewage samples from Schiphol are tested every week. The location is unique. As a busy international airport, Schiphol is a point of entry for people travelling to the Netherlands from other countries, who may be carrying the coronavirus SARS-CoV-2. They may also have a new variant of the virus. For that reason, sewage surveillance at Schiphol Airport mainly focuses on monitoring which variants of the coronavirus are present. 

Results of sewage research at Schiphol

Looking back over the past few years, periods of higher COVID-19 circulation in the Netherlands are accompanied by higher levels of virus particles in Schiphol sewage. Overall, the same variants were observed at Schiphol as in the rest of the world, often also corresponding to similar trends in the Netherlands. The Omicron variant of SARS-CoV-2 was first observed in Schiphol sewage in November 2021. So far, sewage surveillance at Schiphol has only found the same variants that are also found elsewhere. 

Data from Schiphol not displayed on Coronavirus Dashboard or in RIVM open data

Sewage at Schiphol comes from passengers, visitors and employees. It is not a municipal sewage treatment plant that processes household sewage, like the other sewage sampling locations that are included in the sewage figures in the RIVM open data or on the Coronavirus Dashboard. The figures for those locations are converted into figures for 100,000 connected inhabitants. That conversion is not possible for the samples taken from Schiphol Airport. As a result, the data cannot be compared without skewing the results on the Coronavirus Dashboard.