Berlin. “Wastewater is information” – this saying is often heard at the Federal Environment Agency. Excretions from humans and other organisms that end up in wastewater can be analyzed in laboratories. Residues there can provide information about drugs and medication, environmental chemicals and, last but not least, pathogens.
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Such studies have been around for a long time, but it was only during the Corona pandemic that wastewater analyses became known as a tool for monitoring pathogens. A current project by the Federal Environment Agency (UBA) and the Robert Koch Institute (RKI) aims, among other things, to clarify which pathogens should be searched for in wastewater in the future. Experts assume that further epidemics may occur. Then wastewater analyses could reveal the infection process at an early stage and enable countermeasures.
Return of an eradicated pathogen
Actually, such pathogen detection is nothing new: Polio viruses, which can cause polio, were detected in wastewater in the USA 85 years ago. And a few years ago – the pathogens were actually considered eradicated in North America – a wastewater analysis in New York revealed an increased occurrence of polio viruses, whereupon a health emergency was declared there in September 2022.
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It was known that the poliovirus could be detected in the stool of infected people. At the beginning of the Covid-19 pandemic, it was by no means clear that this was also the case with the Sars-CoV-2 virus. In February 2020, Dutch researchers demonstrated that coronavirus DNA could be detected in this way. “Soon afterward, we began to determine whether wastewater was contaminated with coronavirus DNA,” says Hauke Harms from the Helmholtz Centre for Environmental Research (UFZ) in Leipzig. One of his colleagues was a virologist who had already worked with Christian Drosten, which helped to ramp up the analysis.
“As microbiologists, we are used to measuring target substances in complex samples,” emphasizes Harms. But in order to be able to warn early about a new corona wave, a detection sensitivity of 50 infected people per 100,000 inhabitants – i.e. an incidence of 50 – was necessary. This was possible from June 2020. For a long time, monitoring wastewater for health aspects was considered too expensive, says Harms. But the economic damage caused by the pandemic has probably shifted the standards.
Sampling is routine in sewage treatment plants, because there are limit values for many substances in wastewater – the treated water must comply with these. In February 2022, the pilot project “ESI-CorA” started, in which initially 20 sewage treatment plants nationwide and later dozens of other locations analyzed the wastewater for Sars-CoV-2.
The wastewater samples arrive at the MDC well cooled.
Source: Felix Petermann, MDC
Building fundamental structures for the future
Initially, the environmental engineers, chemists and other laboratory staff had no expertise in epidemics. “We first had to learn how to prepare the measurement data and analyses so that doctors could do something with them,” explains Susanne Lackner from the Technical University of Darmstadt. The procedures at the measurement sites also had to be worked out, for example with regard to sample collection, analysis procedures and quality assurance. It was also important to set up a digital infrastructure for processing and quickly forwarding the data.
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“We have created basic structures that will be helpful in future infection events,” says Lackner. It is important to her that politicians create legal certainty regarding the use of measurement data and analyses. Science can prove almost everything that ends up in the water and does not immediately decompose.
The UBA and RKI were already involved in the “ESI-CorA” project, and after its end in March 2023 they joined forces again in the “Amelag” project (wastewater monitoring for epidemiological situation assessment). The UBA is responsible for the technical implementation of sampling and wastewater analysis, for the transport of samples and the flow of information. The RKI takes care of the analysis and publication of data from up to 175 sewage treatment plants.
“Although the infrastructure was created with Corona funds, it will be usable well beyond the pandemic,” emphasizes Ulrike Braun from the Federal Environment Agency. She points out that wastewater monitoring is highly accepted by the population because it provides valuable data, but is also anonymous. So far, it takes up to four days for data to be able to be evaluated. “We should be faster,” emphasizes Braun. Then emerging waves of infection can be identified early on.
The researchers filter the brownish broth, enrich the virus particles they find, isolate and sequence the viruses’ genetic material.
Source: Felix Petermann, MDC
Prioritization of pathogens
The “Amelag” project runs until the end of 2024 – one sub-project is the so-called pathogen prioritization: experts from various disciplines – from wastewater specialists to epidemiologists – are to agree on the pathogens that should be primarily examined in wastewater in the future.
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“The list of possible pathogens is very long,” says RKI employee Timo Greiner. It is important to pay attention to those pathogens about which there is otherwise little information. For example, the health service only learns about West Nile fever when it is severe. As with Covid, wastewater analysis could also determine the number of unreported cases of mild or symptom-free illnesses.
However, it is necessary to check whether and how well new pathogens can be monitored in wastewater. It is also necessary to clarify how often measurements are taken and at which locations. “Wastewater at airports, for example, can contribute to the early detection of introduced pathogens,” explains RKI researcher Greiner. He can imagine that wastewater monitoring could become a pillar of health situation assessment in the future.
A wide variety of pathogens can be measured
In addition to various flu and coronaviruses, antibiotic-resistant bacteria could also be monitored in the future, says Darmstadt expert Lackner. UBA employee Braun also points to the respiratory syncytial virus (RSV).
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It would even potentially be possible to measure trace substances, such as the so-called eternity chemicals PFAS (per- and polyfluorinated alkyl substances). According to Harms, rotaviruses, noroviruses and measles viruses could also be monitored. “In principle, we can measure a wide variety of pathogens, including fungi and protozoa,” emphasizes Greiner.
What is fundamentally possible was recently described by a group led by Markus Landthaler from the Berlin Max Delbrück Center for Molecular Medicine (MDC) in the journal „Environment International“In its study, the team extracted genetic material from samples from a Berlin sewage treatment plant. They found not only common viruses such as RSV or flu, but also seasonal visitors in the wastewater: in spring, viruses that infect asparagus, in autumn, grape viruses, and in summer, viruses that target watermelons or Berlin mosquitoes. “I believe that monitoring wastewater has enormous potential,” says Landthaler.
