Wastewater surveillance into overdrive

Even before the appearance of the SARS-CoV-2 virus last year in the Netherlands, KWR was using wastewater to trace pathogens. ‘Thanks to earlier experience with the isolation of viruses from wastewater, we were able to start immediately with the methods that medical virologists published at the end of January 2020,’ recounts Medema. It was a matter of only a couple of weeks before KWR’s laboratory technicians were able to process the first sewage water samples in the PCR machines. At that point there was nothing to report. One week after the first infections at the end of February, the first peaks in the graphs showed up here and there. At a number of places this happened even before the first patients presented themselves. Medema: ‘The first wave formed right under our noses.’

Objective and efficient

To illustrate that wastewater surveillance offers a valuable supplement in monitoring the spread of the coronavirus in our society, Medema matter-of-factly points out: ‘Not everybody goes to the test lane, but everyone goes to the toilet. The virus particles that we can detect in the wastewater, reflect objectively what is going on within a population. And very efficiently. With a single sewage water sample, you can actually sample a hundred thousand people.’

50 countries, 1000 cities

KWR was therefore the first to use wastewater surveillance as an early-warning system to signal the presence of SARS-CoV-2. ‘We quickly published and communicated”, says Medema. ‘And our work was immediately picked up; from Nature to The New York Times.’ In the meantime, more than 50 countries and 1000 cities all over the world have been sniffing out the virus in their sewage water. Together with the Joint Research Centre of the European Commission, we set up an umbrella research structure grouping the sewage water research of sixty European cities. And together with Michigan State University, KWR is developing a global wastewater data centre with an associated dashboard.

Water and health sectors complement each other

Besides KWR’s molecular expertise, partner collaboration has been a key to the quick success, thinks Medema. ‘To acquire a representative sampling, for instance, we were able to rely on Partners4UrbanWater, the Water Authorities and the Foundation for Applied Water Research (STOWA). But the collaboration with Erasmus MC and the Rotterdam-Rijnmond Municipal Health Authority was also very fruitful. The water and the health sectors can significantly strengthen each other. By linking the data, we can interconnect the above-ground with the underground, so to speak. For instance, at one point we observed that the sewage water of Rotterdam’s Charlois district showed a higher viral load than one would have expected based on the number of people who had themselves tested. This prompted the Municipal Health Authority to introduce test busses to make testing more accessible, so that we could get a clearer picture of the situation in the district.’

New significance of wastewater

Medema thinks it is a good thing that wastewater has taken on an entirely new significance over the last decades. ‘Wastewater, which used to be seen as something that needed to be treated and discharged, has begun to be seen as a source of raw materials. And now it has also become a valuable source of information – a mirror of the society. This has recently become apparent with the virus, but it was already the case in the context of issues such as drugs, pharmaceutical residues and antibiotic resistance. In the future we might also be measuring stress hormones in sewage water, to monitor the mental health of the population.’

Remain alert

The pandemic has put wastewater surveillance in the spotlight, concludes Medema. ‘We have to pursue the collaboration between the water and health sectors. With the emergence of all kinds of coronavirus variants, we need one another. Medical data are indispensable for the detection of new variants. And we frame our wastewater surveillance on the basis of these data. We are able to detect the British variant, and I am confident that we will also succeed with other variants.’ Because people are getting vaccinated and the lockdown is having an impact, the circulation of the virus will be reduced, according to the researcher Medema. But we must certainly remain alert, he says. ‘I expect that sewage will continue to be valuable in the detection of the virus in the months ahead. And KWR has all the means to work with others in keeping a finger on the pulse.’