Text: Erik Freudenreich

Looking at wastewater to prevent future pandemics

Samples from wastewater treatment plants are providing more answers to our scientific questions. Several initiatives in Switzerland want to use these analyses to create a pandemic alert system. Text: Erik Freudenreich

In response to a new wave of cases in China, early this year the European Union came up with novel recommended measures to detect Covid-19: testing wastewater from aeroplanes arriving from the country. The authorities in several countries, including Belgium and Canada, decided to put that into action. In concrete terms, that means taking a sample of wastewater as soon as the aircraft lands and sending it to a laboratory for analysis. The lab sequences the sample to identify the variants present and assess the degree of virus circulation.

The Geneva and Zurich airports have not adopted this measure for the time being. But it is the idea behind a research project launched during the health crisis by Swiss research teams in collaboration with Eawag, the Swiss Federal Institute of Aquatic Science and Technology (see inset). The scientists successfully detected the presence of Covid-19 in wastewater through samples taken during the first phase of the pandemic. Ultimately, the goal is to set up an early warning system. Several initiatives are under way in Switzerland to establish a permanent system of this type.

Understanding the impact

“Wastewater analysis is an interesting approach, which can provide a great deal of information about human activity and its impact on the environment, including the emergence of diseases,” says Marc Augsburger, head of the Unit of Forensic Toxicology and Chemistry (UTCF), which is part of the University Centre of Forensic Medicine in French-speaking Switzerland. This subject has been attracting a great deal of interest from scientists over the past 20 years or so, for a number of reasons. “The first is that wastewater reflects the human activity of a given population area, and analysing it replaces the need to take biological samples from a large number of people.”

It also helps us to better understand and prevent the impact of certain industries and infrastructure. “For example, a hospital delivers a lot of medicine, some of which are toxic to the environment or humans. As these molecules often cannot be filtered by wastewater treatment plants, we need information from wastewater to improve risk analysis and implement measures at an earlier stage in the cycle.”

However, the expert stresses that technical challenges must be overcome. “It’s a more qualitative than quantitative analysis method. That means that the concentrations measured will not be the same after a storm or during a drought.” Moreover, the compounds released in urine have been transformed by the body, which again complicates the calculation of concentration levels. Also, we first need to identify the relevant markers when searching for these substances. “This kind of monitoring is particularly valuable if it is carried out over a longer period. For example, we can detect an increased presence of illicit substances in a given location at the time of a large-scale event such as a music festival.”

Faster decision-making

The Swiss think tank Pour Demain has recently published a study on the benefits of an institutionalised early warning system based on continuous wastewater analysis. Carried out in collaboration with the consultancy Eraneos and the consulting and research firm Infras, the report found that this type of programme could save up to 30 billion Swiss francs in the event of a pandemic in Switzerland.

The study suggests introducing, at 50 to 100 wastewater treatment plants in Switzerland, a continuous monitoring system of five pathogens with the highest pandemic potential: Covid-19, other coronaviruses, influenza viruses, smallpox and measles. This measurement, along with the genetic sequencing of these pathogens found in samples taken from hospitals, medical practices and wastewater, as well as improved management of the data collected to speed up decision-making in the event of a health crisis.

“An early warning system acts like a fire detector or an avalanche forecast,” says Laurent Bächler, Programme Officer Biosecurity at the think tank Pour Demain. “Monitoring pathogens can avoid significant human and environmental economic costs, not only during a pandemic, but also on an everyday basis, for example, by providing better knowledge about antibiotic-resistant bacteria.”

High return on investment

The study examined preparedness for three scenarios: a pandemic similar to Covid-19, a severe pandemic and an extreme pandemic. It measured the human and economic losses avoided from the first detected case of a dangerous pathogen thanks to the preparedness achieved through the early warning system. For example, a lockdown was imposed five to ten days earlier.

“The next pandemic is just a matter of time, with a strong likelihood that it will be more severe than Covid-19,” the authors of the study say. “With annual spending of around 5 million Swiss francs in a normal, non-pandemic year, the investment is low compared to the far-ranging benefits – over a billion Swiss francs in the event of a pandemic similar to Covid-19 and up to 15 to 30 billion Swiss francs for severe and extreme scenarios. Studies from the Imperial College London and McKinsey show that investing in preparedness and pandemic prevention is profitable.”

Political debate is ongoing about whether to adopt such a system. Late last year, the Social Security and Health Committee of the Swiss National Council submitted a postulate requesting that the Swiss Federal Council examine the extension of wastewater surveillance for Covid-19 to other pathogens.
The government was in favour of the motion, which should be addressed by Parliament in the coming months. /

A research project from the Swiss National Science Foundation

What causes viruses to spread? How fast can we identify the variants responsible for a wave? How does a virus become endemic? These are just some of the questions raised by the WISE (Wastewater-based Infectious Disease Surveillance) project of the Swiss National Science Foundation. The project brings together researchers from the Swiss Federal Institute of Aquatic Science and Technology and the École Polytechnique Fédérale in Zurich and Lausanne.

The study began in November 2022 and is developing methods and analyses for monitoring infectious diseases based on wastewater established during the Covid-19 pandemic. Samples are analysed every week at six water treatment plants throughout Switzerland.



In the laboratory in Dübendorf, Switzerland, a staff member places wastewater samples in a freezer at -60°C.

The Department of Environmental Microbiology of the Swiss Federal Institute of Aquatic Science and Technology is interested in monitoring coronavirus levels in wastewater.