The first results of RIVM’s National Wastewater Surveillance show that the novel coronavirus in sewage is decreasing in the Netherlands. This is in line with the decrease in the number of reported patients, hospital and ICU admissions during the research period in April and May. More model-based research is being conducted to better interpret the data on the levels of virus found in sewage. This will facilitate rapid detection and intervention in the event of a possible resurgence of the virus. RIVM will therefore continue its sewage research.

Since the first of April, RIVM has been testing sewage in the Netherlands to map the spread of the novel coronavirus (SARS-CoV-2). Sewage from 29 locations is tested weekly for the presence of the virus. This amounts to a quarter of the Dutch population. Earlier research showed that the virus could be detected in sewage from Tilburg. This was shortly after the first Dutch COVID-19 patient was reported in the Netherlands.


At several locations in the Netherlands, where measurements started at the beginning of March, the study shows that the levels in sewage were increasing, even if no patients were reported at these locations yet. From the beginning of April, the virus has been decreasing in sewage. This corresponds to the decrease in newly reported COVID-19 patients and hospitalisations.  The novel coronavirus in sewage originates from infected persons. This approach offers a less burdensome and more anonymous research method for humans. This makes sewage research an excellent supplement to the research already being done (national surveillance). 


The virus was found at least once in the period April and May at each location studied, for example in the sewage of all the provincial capitals of the Netherlands. The peak in COVID-19 patients admitted to the hospital was in week 12, after which a clear decrease could be seen in each province. The same decrease was also observed in virus levels in sewage at all sampled locations. 

How it works 

The novel coronavirus can be found in the faeces of some of the people who are infected with the novel coronavirus, both in people with and without COVID-19. The virus ends up in the sewage system. Hygienic handling of stools and wastewater is therefore important. See sewage research for more information. The presence of the virus in sewage is being investigated in collaboration with a large number of water boards and district water control boards, a water company and the Union of Water Boards, the virus is being investigated in sewage. At the sewage treatment plant, samples are taken and collected during the course of one full day; some of these samples are sent to RIVM. In the laboratory, the genetic material (RNA) of the virus is extracted and detected.