Testing the Waters: Using Wastewater Surveillance as an Early Warning System

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Dec 13, 2023

Plant engineer Holger Stählke programs automatic sampling at Nordwasser for the examination for pathogens in Germany, March 24, 2022, photo by Bernd Wüstneck/dpa-Zentralbild/dpa/Reuters

Plant engineer Holger Stählke programs automatic sampling at Nordwasser for the examination for pathogens in Germany, March 24, 2022

Photo by Bernd Wüstneck/dpa-Zentralbild/dpa/Reuters

In the months after it was first mentioned in the media almost four years ago, SARS-CoV-2 overwhelmed hospitals around the globe. Over the course of the pandemic, the world struggled to monitor the transmission and evolution of the virus. Solutions like the 'test and trace' tracking apps used in the UK, Germany, and the Netherlands were developed to improve health departments' ability to react and to reduce the impact of mass lockdowns by implementing early, targeted action. Although many of these solutions were expensive and imperfect, the need for better surveillance catalysed a scientific focus on proactive biosecurity measures and improved 'early warning systems' for public health.

Wastewater surveillance is one promising system that was exposed following the discovery that fragments of genetic material from COVID-19 could be identified in sewer water, enabling targeted local action. Spurred by the successes of wastewater surveillance in monitoring the virus, countries like Germany and the Netherlands established their own wastewater surveillance pilots. Others, like Australia, adapted existing infrastructure that had been historically used to detect polio and other viruses. As innovation continues in sampling and sequencing technologies, these pilots are now being scaled nationally—with ambitions to link up globally—as early warning systems for emerging pathogens and diseases. The oft-quoted Victor Hugo line “the sewer is the conscience of the city” has never been more apt.

Such systems were the focus of the International Wastewater Surveillance Conference in Frankfurt on 15–17 November, organised by the Health Emergency Preparedness and Response Authority and the Joint Research Centre of the European Commission in collaboration with a number of other public and charity sector organisations. It pooled the knowledge of many critical stakeholders involved in wastewater surveillance around the world. Their common objective was to develop a roadmap to progress wastewater surveillance by building capacity, assessing need, and generating near-live global data.

Wastewater surveillance is one promising system exposed following the discovery that genetic material from COVID-19 could be identified in sewer water, enabling targeted local action.

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The conference conveyed a shared drive to establish national and global wastewater surveillance infrastructure and data sharing for the good of global public health. Recent RAND Europe research on pathogen surveillance, commissioned by the Novo Nordisk Foundation, points to global fragmentation of surveillance as an important challenge to overcome. The study complements RAND Europe's wider body of work around making early warning systems more effective in dealing with pathogens, including ongoing work on foodborne pathogen surveillance funded by the UK Food Standard Agency.

The Potential of Aviation Data in Pathogen Surveillance

Interestingly, the aviation industry has emerged as a unique player in joining up information. Aircraft waste disposal presents opportunities for pathogen testing. Large numbers of passengers provide a way to assess global trends and movement of pathogens. While it is evident from discussions that we are a long way from global data linkage and surveillance capabilities, involving the aviation industry can act as an initial trigger in enabling a truly international landscape of surveillance.

Within the aviation industry, surveillance and data collection are not without significant challenges. Operational difficulties exist, given the great volume of potential data points. There is potential for false positives and negative press for the industry. Issues around passenger consent and anonymity would need to be overcome, as would the question of loss of anonymity for single-airline routes. Nations are likely to raise concerns around the potential use of this form of surveillance as a border-closing tool, and the requirement for contact tracing creates an innate burden of responsibility which must be clarified. And, of course, there is the question of funding.

Some of these challenges were brought to life in a poignant example of Ebola testing that had been carried out in a study presented by KU Leuven in Belgium, which was met with criticism due to the nature of Ebola. Clinical manifestations would appear either before, or in sync with, wastewater surveillance, rendering positive tests a cause for alarm rather than an early warning.

Despite the challenges, however, the potential of the aviation sector for establishing data platforms and information-sharing mechanisms cannot be ignored, given its global expansiveness and international remit.

Wastewater Surveillance Could Support Metagenomic Approaches

The conference showcased many surveillance initiatives across Europe, Africa, and India. However, establishing wastewater surveillance for bespoke pathogens only is a missed opportunity, diminishing its usefulness as an early warning system. Metagenomic approaches, which test for multiple biological agents, should instead be developed in close consultation with clinicians and epidemiologists to ensure that the surveillance infrastructure can act not only as an early warning system for public health, but also for national biosecurity, enabling broader threat detection. Futureproofing these mechanisms and making them sustainable would mean that infrastructure doesn't need to be developed from scratch every time there is a biological threat to public health.

Further discussions are needed on technical approaches to sampling and sequencing to showcase the value and feasibility of wastewater surveillance in different settings.

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Further discussions are also needed on technical approaches to sampling and sequencing to showcase the value and feasibility of wastewater surveillance in different settings. More research and sharing of knowledge needs to be enabled within this community so standards and protocols can be developed, replicated, and scaled. Sampling and testing approaches to surveillance will be different in busy travel ports compared to countries that don't have a traditional sewage system, which will affect how protocols are developed and applied elsewhere. More use cases would help with this so that best practices can be shared and agreed.

Gaining the necessary numbers of samples can be difficult, but ideas are emerging that combine representative sampling with computer modelling. Using software to predict prevalence and incidence of particular pathogens from a relatively small sample can help to counter lack of volume. This is already being used in the busy travel port of Singapore and could also be useful in Germany, for instance, whose 9,000 wastewater treatment plants make comprehensive sampling coverage a tall order.

Next Steps

Despite the challenges surfaced, the global conference ended on a hopeful note, with the establishment of a global consortium to fund sentinel and community surveillance systems and enable global data sharing. This is a promising endeavour and the consortium has a huge responsibility to ensure that its funding and outputs truly move the dial on wastewater surveillance as part of the broader biosurveillance toolkit.

It will be critical for the consortium to ensure that its funding is used to establish systems that can adapt and pivot to new pathogens and adopt metagenomic approaches to act as an early warning and detection system, nationally and globally. The consortium will also need to ensure that meaningful progress occurs on the data sharing and linking front, perhaps starting with aviation. Lastly, wastewater surveillance efforts are already underway, so acknowledging what already exists is a crucial first step. Success will require bringing together the knowledge being amassed to combat the fracturing of pathogen surveillance and to enable effective early warning between countries.


Sana Zakaria is a research leader at RAND Europe.