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Wastewater sampling to play more prominent role in monitoring development of coronavirus

The COVID 19 pandemic has entered a new phase. Coronavirus has not gone away, but it no longer presents an immediate burden on the healthcare system. In many cases, testing by the municipal health service (GGD) is therefore no longer necessary. This means that the number of positive GGD tests has become less useful as an indicator for tracking the spread of the virus.

Instead, wastewater sampling will play a more prominent role in this regard, along with a number of other methods. Below, we explain why it remains important to track the spread of the virus, what role wastewater sampling plays and how we are reflecting this on the Corona Dashboard.

As of 11 April 2022, it is no longer necessary to have a positive self-test confirmed with a test by the GGD. From now on, the GGD will only test certain groups of people, such as those who require proof of recovery or people who live in care facilities. The drop in the number of people undergoing PCR tests by the GGD means a decline in the number of confirmed cases and a change in the percentage of people who test positive. These figures are therefore no longer as suitable as they were for tracking the virus’s spread and development.

Virus particles in wastewater
It remains important to continue tracking the spread of coronavirus, however. Tracking allows us to anticipate new outbreaks before they happen and recognise and respond quickly to new variants. Wastewater sampling is a good way to do this. When people are infected with coronavirus, virus particles can be found not only in their nose and throat, but are also shed in their faeces. This is true for everyone, whether or not they have symptoms or get tested. The amount of virus particles in wastewater has recently been shown to be a good indicator of the spread of the virus. An increase or decrease of particles shows whether there are more or fewer people infected with coronavirus. Read more about wastewater sampling on the website of the National Institute for Public Health and the Environment (RIVM).

This image gives a view on the process of the sewage research. The steps are in de following order: collecting the samples, take them to RIVM, make preparations for analysis, extract RNA, detect PCR and other research for COVID variants, data analysis and modelling, adding data to the Coronavirus Dashboard.

Survey data and data from doctors and hospitals
In addition to using the data from wastewater sampling, the government uses health data from surveys of people who have volunteered to provide their data through the Infectieradar website. The government also uses data RIVM has collected from general practitioners about people with flu-like symptoms. Hospital and intensive care unit (ICU) admissions also offer a good indication of the virus’s development.

Samples taken 3 times a week from 300 wastewater treatment plants
RIVM receives wastewater samples from over 300 wastewater treatment plants across the Netherlands three times a week. The more than 1,200 samples collected per week are tested in the RIVM lab for coronavirus particles. The data from this can be found on the Virus particles in wastewater page of the Dashboard.