Monitoring of coronavirus-RNA (SARS-CoV2) in sewage: an early warning system

KWR Water developed a method to monitor the presence of the Coronavirus (SARS-CoV2) in sewage. Whereas the testing of individuals requires individual tests, testing the sewage can give an early indication of the contamination within a whole population (city).

What are the steps?

1. Over a 24 hours period, we collect sewage samples at the waste water treatment plant of  a city. The samples are safely brought to the KWR labs.
2. Waste water always contains high concentrations of viruses. The question is whether SARS-CoV2 is also present. In the lab, we concentrate the particles present in the sewage through centrifugation.
3. The genetic material – RNA – forms the basis material for further testing the presence of SARS-CoV2.We first isolate the RNA from the virus particles and purify it. We can now start testing if SARS-CoV2 is present.
4. High concentrations of different viruses and other microorganisms are present in sewage, the concentration of SARS-CoV2  is very low. An amplification step is used to specifically multiply a fragment of SARS-CoV2 RNA to be able to detect the low concentrations of SARS-CoV2 RNA. This amplification step is called RT-PCR.
5. If SARS-CoV2 is present in the waste water, the multiplication step will result in an increased concentration of a SARS-CoV2RNA-fragment. This increase is visualized as an amplification curve as displayed on the monitor screen.
6. Samples with no SARS-CoV2 RNA show a flat line. The 3 curves show the results of various waste water samples containing SARS-CoV2 RNA. The graph shows 4 different samples (1 without SARS-CoV2and 3 with SARS-CoV2).The earlier the curve appears (more to the left) the higher the concentration of SARS-CoV2in the sample and the higher the infection grade within the population can be expected.