Insights from the COVID-19 period

Coronavirus monitoring in sewage research

RIVM has been researching trace amounts of pathogens in Dutch sewage for years. During the outbreak of the coronavirus SARS-CoV-2 in 2020, sewage research received much more attention. Development on this type of research also accelerated dramatically. Sewage research continues to help us monitor the coronavirus. 

Important to keep track

The coronavirus SARS-CoV-2 now poses less of a threat than it did initially. This is due to the vaccinations and previous infections in the Dutch population, and because the Omicron variants are less likely to cause severe illness. Despite that, keeping track of the virus remains important. As a result, we know how often the virus occurs and where the virus is spreading, especially if it is spreading rapidly. We also know which variant is circulating, and whether a new variant is emerging. Sewage research is a very important part of this. Analysing sewage offers a very good impression of how the virus is circulating among the population. We all use the bathroom, and almost all households in the Netherlands are connected to the sewage system.

Virus particles in sewage

Human faeces from people who have COVID-19 can contain virus particles. Working with the regional water boards in the Netherlands, RIVM set up a program in which sewage samples are taken several times a week from all 300 sewage treatment plants in the country. Read more about how this research works and check out the answers to frequently asked questions on the page about coronavirus monitoring in sewage.

Also key to tracking down other diseases

Sewage research is not new. Many diseases that occur in a group of people can be detected in sewage. This could involve infectious diseases like COVID-19, but can also be used for non-infectious diseases. RIVM has been screening sewage for the poliovirus for 30 years now. Bacteria that are resistant to antibiotics are also found in sewage.

International partnerships in sewage research

RIVM has over 30 years of experience in sewage research. Within the European Union (EU European Union (European Union )), RIVM is considered an expert in this field. Other countries rely on RIVM expertise in the course of setting up and carrying out the research, and contact RIVM about data collection, analysis and modelling. The project has also been launched to expand this collaboration with other countries in the EU. Willemijn Lodder, senior researcher working in sewage research at RIVM: “This may contribute to helping us be better prepared for any subsequent pandemic. We are also exploring whether we can deploy sewage research on broader scale.” 

A virus changes constantly. The coronavirus SARS-CoV-2 is also constantly changing slightly. There are already many different variants. To monitor which variants are circulating in the Netherlands, RIVM has been examining samples containing the virus since the start of the pandemic. 

In the laboratory, all the building blocks of the genetic material from the virus (RNA) are mapped. These building blocks are compared to those of other samples. This research is known as pathogen surveillance. This shows whether the virus is changing and how. It also helps us determine if we need to be more alert regarding certain variants. We can also see how different variants of the virus are related and how they are spreading. 

Changes in the virus

This research is important to know whether the new variants that are circulating have characteristics that pose additional risks. Some changes (mutations) can cause a variant to spread more quickly or make people more ill. Other mutations change the external appearance of the virus. This makes it harder for the immune system to detect the virus after a previous infection or vaccination. 

Partnerships

In the early phase of the pandemic, most of the samples came from the test lanes operated by the Municipal Public Health Services (GGDs). At the peak of the pandemic, this involved up to 1,500 samples a week. RIVM also partnered with about 45 laboratories across the Netherlands. The laboratories submitted a random sampling of test samples for research purposes every week. The GGD test lanes are closed by now, so the samples that are tested by RIVM primarily come from hospitals or general practitioners. In total, more than 160,000 COVID-19 test samples were examined during the course of the pandemic. 

International

RIVM also maintains contact with other countries that perform pathogen surveillance. Thanks to this international network, RIVM is also aware of which variants are circulating worldwide. As a result, we can take appropriate action if, for example, a new and more contagious variant is discovered. This is how the Omicron variant was first discovered in South Africa. Because this variant was much more contagious than the variant before it, we knew that Omicron would eventually become the dominant strain in the Netherlands as well. Nearly 1,000 different variants of the coronavirus SARS-CoV-2 have been found worldwide. Dirk Eggink, virologist at RIVM: “The COVID-19 pandemic made it necessary to invest in innovative techniques and in training new employees. These investments made it possible to conduct this variant analysis research.” Read more about pathogen surveillance.