The COVID-19 pandemic saw many countries successfully track the spread of the disease by sampling wastewater. The United Nations Environment Programme (UNEP) has been evaluating the impact of the pandemic on the water sector and contributed to the dialogue around wastewater surveillance as an early warning tool to track community transmission of COVID-19.
Wastewater contains bacteria, viruses and pathogens excreted by humans. Surveillance can therefore be a valuable public health tool for monitoring the spread of infectious diseases such as flu, cholera, monkeypox and typhoid.
According to a recent study, surveillance enables rapid pathogen detection and community prevalence quantification. It can help identify potential hotspots of antimicrobial resistance by tracking the concentration of antibiotics in wastewater.
We sat down with UNEP wastewater expert Riccardo Zennaro to learn more.
What has been the impact of the pandemic on the water sector?
Riccardo Zennaro (RZ): The COVID-19 pandemic added additional pollutants to wastewater. The risk of antimicrobial resistance also increased due to an excessive use of soap, cleaning agents, disinfectants, and increased use of antibiotics. Ineffectively treated wastewater also led to the leakage of huge quantities of single-use plastics into water bodies. The pandemic has also forced the water sector to be more agile and flexible and make greater use of digital solutions to boost water security, resilience and explore innovative ways of predicting the spread of the virus. In addition, the pandemic also saw the increased use of wastewater surveillance as a sentinel for the spread of COVID-19.
What’s the point of wastewater sampling? What can it tell us?
RZ: Wastewater sampling has been used for a long time to detect diseases like polio. By monitoring wastewater from homes and hospitals, public health authorities can cost-effectively gauge the extent to which a disease might be circulating in a community, without solely relying on data from people using health services. During the pandemic, monitoring and surveillance of wastewater became important in detecting possible waves of COVID-19 and other diseases. Wastewater surveillance programmes are globally expanding after COVID-19 and helping to put a spotlight on wastewater, which for too long has been neglected.
To what extent can wastewater surveillance, also known as wastewater-based epidemiology, predict the outbreak of diseases?
RZ: It a useful tool that can complement other research. There is evidence that it can provide early warning signs of the presence of diseases within a community. Wastewater sampling can help scientists better assess the risks of a disease becoming more prevalent. Early warnings allow timely public health interventions to prevent or control the spread of a disease.
What about the value of wastewater surveillance in places where there are no formal sewage systems?
RZ: Research into wastewater-based epidemiology to evaluate the level of circulation of the virus in a population has been stepped up in both on-grid and off-grid sewage systems. One very recent study from southern Israel says, “sewage surveillance... can be a critical aspect of outbreak surveillance and control in areas with insufficient human testing and off-grid communities.” Globally, 44 per cent of household wastewater is not safely treated. Huge quantities of wastewater including from agriculture and industry, go untreated into the environment, polluting both fresh and saltwater bodies.
Is surveillance gaining momentum worldwide?
RZ: Absolutely. A 2022 study notes that wastewater-based epidemiological surveillance interventions and programmes for monitoring the spread of COVID-19 had taken place in at least 55 countries. This is something very positive and encouraging for the future of our health systems and environment.
How is UNEP promoting wastewater surveillance?
UNEP was involved in a side event focusing on wastewater surveillance at the recent UN 2023 Water Conference in New York to take stock of what has happened worldwide so far and look to the future. The achievement of safe drinking water and sanitation will be a major focus at the High-level Political Forum in July 2023 and I believe these efforts are critical to advancing Sustainable Development Goal 6 to “ensure availability and sustainable management of water and sanitation for all.” UNEP will continue to support these dialogues and highlight the importance of wastewater surveillance including at major events this year, such as World Water Week in Stockholm in August.
What are the priorities right now?
RZ: Some parts of the world have benefited from good practices and significant efforts to monitor and assess water quality. But for others, the opposite is the case. We know that surveillance is a powerful tool for both public health and the sustainable management of natural resources. I think the focus now should be on capacity-building, knowledge transfer and awareness-raising. In the spirit of implementing the One Health approach to ensure systems thinking in sound environmental management and public health, UNEP will continue to support these efforts.
UNEP is supporting Member States and others to address issues such as pollution through the World Water Quality Alliance, the Global Partnership on Marine Litter, the Global Partnership on Nutrient Management and the Global Wastewater Initiative (GWWI). With GWWI partners, UNEP is working to highlight that wastewater is a resource that can boost water security and that low-cost alternative wastewater treatment systems can be a viable solution if conventional systems or upgrades are not feasible.
For further information, please contact: Riccardo Zennaro: riccardo.zennaro@un.org
