The relaxation of the pandemic-related restrictions harbors the risk that new outbreaks and foci of Covid-19 will appear in the coming weeks and months. That is why a project is now starting in Germany that should identify such corona hotspots early – on Sars-CoV-2 in wastewater. Because studies show that infected people excrete the coronavirus through the faeces and that these viruses can then be detected in the wastewater. This evidence could therefore help to identify early outbreaks. From mid-May, scientists in 20 German wastewater treatment plants will begin a test run of such virus monitoring using wastewater.
The problem is unreported: it is now known that many people infected with coronavirus do not notice their infection at all because they develop only mild symptoms or no symptoms at all. This makes it difficult to recognize and contain the risk of infection and new outbreaks in good time. At the same time, the capacity of the test laboratories and the staff is not sufficient to regularly test the entire population or just certain groups. But there could be a remedy. From examinations of patients with Covid-19 it is now known that Sars-CoV-2 affects not only the respiratory tract and lungs, but also other organs, including the intestine. The latter leads to diarrhea and nausea in around a third of the patients and raised the question of whether the faeces of Covid 19 patients could be infectious. So far, this has not been clearly proven, but it is clear that infected people excrete the coronavirus with their faeces and urine – and probably even if they develop only mild symptoms.
Corona virus can be detected early in waste water
As early as March 2020, various research groups proposed to use wastewater tests on Sars-CoV-2 for the early detection of new sources of infection. “Such real-time detection could determine whether there are Covid patients in an area and thus quickly enable further tests, quarantine and other countermeasures,” said Zhugen Yang from Cranfield University in a publication. A study by Dutch scientists suggests that wastewater monitoring could also work in practice. From mid-February 2020, they had regularly taken wastewater samples at Schiphol Airport and several other sewage treatment plants and examined them for Sars-CoV-2. In fact, as of March 2, they were able to detect the virus’s genetic material in the wastewater samples – four days after the first Covid-19 case was reported in the Netherlands. The sensitivity of the tests was so high that the researchers were able to detect the presence of fewer infected people per 100,000 inhabitants.
Based on this previous experience, German scientists and authorities now want to use wastewater as an early warning system in the corona pandemic. A team of more than 20 wastewater experts, microbiologists, virologists and modelers from several research institutes and universities has been working for several weeks together with the wastewater treatment plant operators in the cities of Cologne, Leipzig, Dresden, the Eifel-Rur water association and a further 20 cities to determine the overall degree of infection from representative wastewater samples in the catchment area of sewage treatment plants. Now they are ready to test the practical application in a first pilot phase: “In the second half of May we will carry out a test phase together with around 20 sewage treatment plants, which will cover the entire analysis chain, from the taking and preparation of the samples to the PCR analysis and model projection includes ”, reports the initiator of the project, Georg Teutsch from the Helmholtz Center for Environmental Research (UFZ).
Daily samples in 900 sewage treatment plants would suffice
The scientists hope that nationwide wastewater monitoring can help prevent a new wave of infection and monitor the consequences of the easing measures for the spread of the virus. According to your calculations, it could be sufficient to take samples from around 900 sewage treatment plants in Germany every day. That would cover 80 percent of the total wastewater flow and thus a large part of the population in Germany. “If the wastewater monitoring works and can be implemented nationwide, there is huge potential for dealing with the current Sars-CoV-2 pandemic – and prospectively also for comparable future pandemics, because it collects and processes valid data on the so-called epidemic of the population can ”, Saxony’s Minister of Science Sebastian Gemkow commented on the start of the new project.
It is important for the success of such coronavirus monitoring by wastewater that the test methods can reliably detect the presence of Sars-CoV-2 and with a sufficiently high sensitivity. “The decisive factor will be the ability to achieve a detection sensitivity for Sars-CoV-2 that does not only provide usable results for large numbers of infected people,” says virologist René Kallies from the UFZ. “However, initial results make us cautiously optimistic that the intervention management will fall below the limit of 50 infected per 100,000 inhabitants.” This limit was recently decided by politicians as a threshold from which loosening would have to be withdrawn locally and stricter precautionary measures introduced in order to be implemented contain the outbreak. In order to achieve this accuracy of detection, the wastewater samples must be concentrated and processed on viral RNA before analysis. As part of the project and the pilot phase, three preparation methods will be used in parallel and tested for their performance: freeze drying, column filtration and the so-called polyethylene glycol precipitation. At the same time, researchers are working on building the model systems for a planned continuous data flow. The scientists then want to determine as soon as possible whether this succeeds and which analysis protocol proves to be suitable in the test phase and inform the public.
Source: Helmholtz Center for Environmental Research – UFZ