All that's left behind
To archaeologists, a bit of rubbish can be a gold mine. The smallest shard of pottery, piece of bone or scrap of leftover food can tell us a great deal about everyday life in a society. It’s a similar story with wastewater. In that sense, you might describe the work being done by Christoph Ort and Tim Julian as that of archaeologists on a modern-day dig. By analysing what people leave behind, they can find out more about what’s happening to society in the here and now.
Health data in wastewater
Their method began life as a way to identify drug residues in wastewater. Ort was able to show how effective wastewater analyses could be in supporting national drug monitoring programmes. However, the method really gained traction during the COVID-19 pandemic, since viral genetic material can also be identified by analysing traces in wastewater. Just like drug residue, this material is excreted into the toilet and eventually ends up in sewage treatment plants. “Wastewater is extremely valuable,” says Julian, who founded the “Pathogens and Human Health” research group at Eawag a decade ago. “It’s a treasure trove of health data.” And this wealth of information is just waiting to be analysed.
The importance of wastewater post-pandemic
The project is being supported by the Federal Office of Public Health and remains topical even in a post-pandemic world because while the coronavirus may have all but disappeared from public consciousness, it is still an issue for sewage treatment plants.
“Switzerland is a country that still monitors its wastewater for traces of coronavirus even though the pandemic is over,” explains Ort, an environmental scientist. The value of these methods is not lost on the public authorities; at the height of the pandemic, wastewater from up to 100 sewage treatment plants was being analysed. The scope has narrowed since then, with 14 plants currently being monitored. The plants have automated processes for taking routine water samples, some of which are sent to Dübendorf to be analysed in the Eawag laboratory. Alongside COVID-19, the monitoring process covers a range of other infectious diseases, including influenza, RSV and MRSA bacteria, which are resistant to some antibiotics.
Environmental surveillance
Searching for pathogens in the environment as well as in hospitals is not a new concept, says Julian, a microbiologist. In fact, people have been talking about the idea of “environmental surveillance” for quite some time. However, to monitor the environment like that, you need to find the right spot to position your sensors. Experts have been championing the establishment of wastewater-based epidemiology for over a decade. The method has long been on the periphery, Ort adds, but now that it has proven just how useful it can be, the breakthrough may have come at last.
Function of an early warning system
Virus monitoring provides access to a second source of data, allowing experts to keep track of the viral load away from the clinical environment. This method is also independent of current test procedures, which have a major influence on the data available from hospitals, testing centres and doctors’ surgeries. In these scenarios, the more tests that are carried out, the more infections are identified – and vice versa.Wastewater presents a more “neutral” option.
The close collaboration with researchers at ETH Zurich and EPFL has made it possible not only to determine the viral load, but also to track the development of variants. So, with the sensors now in place, the question is: Would it be feasible to establish a kind of early warning system, using wastewater analyses to track the progression of certain diseases before they become an issue for the healthcare sector? “In theory, yes,” says Julian, “there are ways to sequence large amounts of unknown DNA.” But these are highly complex processes, so it’s still too early to say how this would work in practice.
New perspectives in terms of public health
That said, what we can do now is establish connections between virological and pharmacological analyses. It’s not just drugs and viruses that can be tracked in wastewater; we can also detect cough syrup and histamine blockers that are linked to allergies. This opens up an array of new perspectives in terms of public health. It essentially allows us to track symptoms in real time across the population and establish correlations that might otherwise have gone undetected. Demand for these kinds of data is growing. However, Ort also stresses the importance of ensuring that the information obtained is “handled with care”.
