Together with the water boards, RIVMNational Institute for Public Health and the Environment is currently testing sewage samples for the presence of the novel coronavirus. This involves a total of more than 300 sampling points at sewage treatment plants throughout the Netherlands. Sewage from all of the over 17 million people in the Netherlands is being checked for the coronavirus. In recent weeks, the levels of virus particles have been increasing in some regions, but seemingly not in others.

The results of the sewage research can now be found on the Dutch Government’s updated coronavirus dashboard. The data on the dashboard is updated on a weekly basis. Sewage monitoring has expanded considerably in a short period of time: from 29 sampling points in April, to 80 in July. And now all of the more than 300 locations are being monitored on a weekly basis.

Latest results

In August, an increase could be observed in national coronavirus levels in sewage compared to the period before. This concerns the number of virus particles per millilitre of sewage. RIVMNational Institute for Public Health and the Environment is currently seeing differences from one region to another. At most sites, no coronavirus particles are detected in sewage samples. However, there has been an increase in recent weeks at other sites, such as Amsterdam, Almere and The Hague. In the past week, there were two peaks in Leiden North and Woerden. 

Researchers test sewage samples that have been collected over a 24-hour period once a week. The test results show how many virus particles are present in the sewage. Not all people who have COVID-19 also have detectable virus particles in their faeces. Some people who are infected with the novel coronavirus have higher levels of virus particles in their faeces than others. These levels are not determined by whether a person infected with the novel coronavirus has many or few symptoms, or is asymptomatic or presymptomatic.

Differences by region and by sample time

The number of virus particles in the sewage can vary regionally and by region and at different points in time as a result of the constantly changing number of people who are excreting the novel coronavirus. Also, the sewage that enters the treatment plants in which samples are taken does not only come from households, but is often mixed with wastewater from companies. In addition, rainwater dilutes household sewage. RIVM is working on a method that provides insight into these differences to facilitate better comparison of the data from different regions.

To prevent the virus from continuing to spread, it is important for people to comply with the measures. Keep your distance. Work from home as much as possible. If you have symptoms, stay home and get tested. Wash your hands frequently, and in any case when you arrive at home, after using the toilet, and before preparing food. Sneeze and cough into your elbow.