Sewage water shows developments in the corona pandemic

Especially in the initial phase of the epidemic that has lasted for a year and a half, the corona tests administered did not provide a good picture of the precise infection rate in the Netherlands. This was because testing capacity was still limited. KWR developed a test method to measure trends in corona infections based on samples from sewage water. We spoke to Goffe Elsinga, analyst at KWR, about this methodology.

By: Dimitri Reijerman

While the first test streets still had to be built at the beginning of 2020, KWR had been busy with the first measurements for months, says Elsinga: “We have been working on detecting corona in sewage water for a year and a half. Professor Gertjan Medema of KWR has previously conducted research into the presence of viruses in sewage water. During the SARS outbreak of 2002-2003, an article was published showing that infected people also pass this virus into the sewer through their feces. Medema thought that this could also be the case for SARS-CoV-2 and that it would be interesting to monitor this in the Netherlands. The thought was that it could be a good way to monitor the level of contamination.”

He continues: “We started the first measurements in mid-February 2020. Then we took the first samples in a number of cities and these were extensively analyzed for the presence of corona. That was before the major outbreak in the Netherlands in March 2020. We now monitor in a number of neighborhoods in Rotterdam, as well as in Amsterdam and Utrecht. We do that every week, except in Rotterdam, where we do it three times a week.”

Methodology

Elsinga explains how the search for COVID-19 in sewage samples works: “We use the RT-PCR primer sets from the American CDC. We still had to optimize the method a bit before it could be used for testing sewage samples. We use the digital droplet PCR (ddPPCR) and primer sets from BioRad to detect specific corona variants.

“With this ddPCR method we can better detect the mutations of the various corona variants. For example, we managed to identify the Alpha variant in December 2020. With this method we were able to clearly demonstrate the increase of this variant in the following months. We can now also detect the Delta variant via an indirect method. You have to pay close attention to specific mutations of the virus.”

Cooperation

KWR researchers work closely with health authorities in their measurements: “We publish the data, but at KWR we also work with the GGD in Rotterdam and the Erasmus MC,” says Elsinga. “The samples are also sequenced at Erasmus to see if there are any more variants present. Our data is also compared with the data available on the number of corona tests administered and the number of hospital admissions. Ultimately, this should lead to a publication, but our research is still ongoing.”

Future

All in all, Elsinga thinks that such research is here to stay: “I think that more and more similar research will be conducted into sewage water in the coming years. You can get so much information from it. For example, we also conduct research into drug use, which you can also remove from the sewer. There is still a lot to do.”