Sewage as an indicator of health

For more than 20 years, RIVM has been examining sewage for traces of pathogens and other substances to gain insight into the health of people living in the Netherlands. More recently, COVID-19 has led to the establishment of a National Sewage Surveillance programme. Apart from coronavirus monitoring, RIVM examines sewage samples for pharmaceuticals, poliovirus and antibiotic resistant bacteria. And there are many more plans for the future.

As Ana Maria de Roda Husman confirms, “Broadening to include lifestyle and non-communicable diseases such as diabetes is definitely possible.

“As early as 1997, we were on the lookout for the norovirus in sewage near nursing homes,” says Ana Maria de Roda Husman, head of Environment at the Centre for Zoonoses and Environmental Microbiology. Though this research is not new, it was the emergence of the coronavirus SARS-CoV-2 that led to the establishment of the National Sewage Surveillance for coronavirus monitoring. All of the over 300 sewage treatment plants in the Netherlands are already taking part. The surveillance programme is implemented in close cooperation with the Union of Water Boards and the regional water boards. 

COVID-19 requires sewage samples to come in twice a week from all treatment plants. The samples are examined at the Z&O laboratory. Ana Maria de Roda Husman explains, “The virus is first detected in human faeces before people show any symptoms. Virus particles can be found in the faeces of about half the people carrying the coronavirus, and then enter the sewage system when they use the toilet. 

Sewage can tell us a lot about the spread of the virus. Even with the current level of widespread testing, this research is still useful. We have seen levels dropping in the past weeks*, but there are also locations that have shown an upward trend.” Data on this can be found on the Corona Dashboard provided by the national government. This shows the levels of virus particles detected in sewage per area, expressed in terms of number of particles per 100,000 people.”

*This was in March 2021

Diabetes and stress

Viruses or bacteria are not the only things that can be traced by examining sewage samples. Ana Maria de Roda Husman continues, “There are all sorts of things we can learn from the substances found in faeces or urine discharged into the sewage system. We can detect pharmaceutical residues and drug use, but sewage can also provide indicators of stress and lifestyle factors. Sewage research can also reveal non-communicable diseases, such as diabetes and specific types of cancer. We are not yet exploring all available options, but with the infrastructure now in order, we can broaden our scope.”

Together with parties like the Ministry for Health, Welfare and Sports, the Foundation for Applied Water Research (STOWA), the regional Water Boards, the Union of Water Boards and others, RIVM is exploring the possibilities. “The beauty of this research is that it is RIVM-wide. Health, environment and infectious diseases, it all comes together,” De Roda Husman states. “A healthy living environment is a fine example of such a broad subject. If there is any change in the living environment or if people change their lifestyle, we might be able to tell through sewage research.”


Sewage surveillance has advantages compared to other types of research. De Roda Husman assures, “People's anonymity is safeguarded. It is objective. There is no need to bother people; it is a low-impact form of research in terms of direct contact. And nearly every Dutch household is connected to the sewer.”

“If people change their lifestyle, we might be able to tell through sewage research.”

Sewage research offers improved opportunities for formulating signal values, such as the current indicators for positive test results and hospitalisations. For example, what levels of virus particles detected in sewage require immediate action? “With COVID-19, as with anything else we research in sewage surveillance, the aim is to measure a value that triggers action, not just nationally but at a local level as well. And this should be connected with other indicators, such as positive test results. This could lead to a framework for action for the Municipal Public Health Services (GGDs), such as additional testing. This work is still ongoing.”

Viewed in connection

Sewage research is not an isolated entity. It works well in connection with other monitors, which leads to proper interpretation of information. “Medication residues in sewage should be seen in connection with the medication that is being sold. Survey questionnaires covers part of the research for other topics, which sewage research constitutes another part. Combining all the information gives the clearest picture.” “Sewage research is also a great predictor,” De Roda Husman says. “In the summer of 2020, figures for confirmed cases of COVID-19 were low, but we could already see local increases in coronavirus in the sewage.”

Would you like to know more?

Would you like to know more?