After the Lee Kuan Yew Water Prize: Gertjan Medema accelerates the development of wastewater surveillance

When Medema accepted the cash prize of S$300,000, more than 200,000 euros, and the gold medal two years ago, the coronavirus pandemic had only just ended. The researcher received the award for his groundbreaking SARS-CoV-2 wastewater research, which laid the foundation for global public health surveillance.

Global measurement infrastructure

“When the pandemic broke out, everyone jumped on it,” Medema recalls. “It became clear quite quickly under what conditions wastewater could be used to detect the coronavirus and to see how it was circulating among the population. This led to the creation of a global measurement infrastructure for the virus, in which 70 countries took part. Of course, that gives you something extremely valuable, and the question naturally arises: what else can we do with this?”

Bringing fragmented knowledge together

Medema observed that, for other infectious diseases that may possibly be detected through wastewater, knowledge development is quite fragmented. “In one country, measles appears; in another, the Zika virus. There is no joint knowledge development around wastewater epidemiology for virus detection in wastewater, as there was at the time for the coronavirus.” Since KWR, as a Collaborating Centre on Water Quality and Health, has close ties with the WHO, it was decided to invest part of the Lee Kuan Yew Water Prize in compiling guidelines for wastewater surveillance for infectious diseases that are suitable for this purpose.

Broad spectrum of infectious diseases

Medema cannot say exactly how many infectious diseases can now be detected through wastewater. But it is a very broad spectrum. “It is not only about respiratory infections, such as coronavirus, influenza and RSV. It also includes intestinal infections such as norovirus, adenoviruses and enteroviruses. Even a skin condition such as scabies can be detected in wastewater. As can measles, cholera and typhoid. And also the Zika virus, which is spread by mosquitoes.”

Demonstrating added value

Using an example, Medema explains how important it is to compile guidelines for all possible infectious diseases that are suitable for wastewater surveillance. “With measles, doctors are quick to say: you can see that disease very clearly in people, so why would you look in wastewater? Yet in South Africa, for example, part of the population remains under the radar. If you live in a slum, you do not go to a doctor. If, in such a case, you also look at the wastewater, the signals are picked up. The point is that, with the guidelines, we demonstrate the added value of wastewater surveillance for health authorities. That this deserves a place in the whole spectrum. Classical clinical surveillance carries the risk of ‘silent transmission’: the phenomenon of a disease spreading among the population without this being noticed. With wastewater, you have an objective measurement system at your disposal. That is how we want to help public health.”

Workshop: taking steps towards implementation

During this year’s SIWW, Medema returns to Singapore to share the efforts of the past period with the global water community. And to show that wastewater surveillance can do much more than measure SARS-CoV-2. During a workshop, which he is giving together with the WHO, the guidelines for wastewater surveillance that have been drawn up since 2024 for various infectious diseases will be reviewed. And this number is still increasing. “The guidelines contain the current knowledge on best practices, strengths and weaknesses, and what to pay attention to. For example, you need to know how to distinguish the actual virus from the vaccine in wastewater. The workshop is intended to show concrete examples from practice. Singapore, for instance, will give a presentation on the role of wastewater surveillance during the Zika virus outbreak. For the first time, we are sharing the public health value of this technology on such a large scale. And I hope that this will allow us to take steps towards implementation.” In addition to the workshop, Medema also mentions the launch of the latest edition of the WHO Guidelines for Drinking-water Quality as an important highlight during the SIWW congress.

Warning system

Looking to the future, Medema would like wastewater to also be able to function as a warning system that helps prevent the next pandemic. “Hotspots of infectious diseases occur all over the world,” he says. “If you look back at 2020, with SARS-CoV-2 we did not know at the time what we should be looking for. It was as if you were searching for a needle in a haystack without knowing what that needle looked like. How valuable would it be if you could see when a virus is coming our way? If you could tap that knowledge from international transport systems of people, and also animals? Together with Erasmus MC, we are looking at the possibility of picking up signals in wastewater before the symptoms of an infectious disease become visible. In this way, we hope to learn to recognize the contours of an upcoming virus outbreak at an early stage.”

Same scientific field awarded again

Medema is pleased to see that, during this year’s SIWW, his knowledge field is once again receiving recognition. The American researcher Joan Rose, also a KWR Honorary Fellow since 2016, is receiving the Lee Kuan Yew Water Prize 2026 for her groundbreaking work on the development of quantitative microbial risk assessment (QMRA). Medema has known Rose for 35 years and praises her inspiring pioneering work in research into microbiology, water quality and health, as well as her strong social commitment. “The way we look at the safety of drinking water in the Netherlands is partly inspired by the work of Joan Rose,” says Medema. “This development has led, among other things, to the Analysis of Microbiological Safety of Drinking Water, which is included in the Dutch Drinking Water Act. With her passionate approach, she is an example for the new generation.”