Since December 2019, the severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) has infected more than two million people across the globe, claiming, at the time of this writing, more than 300.000 lives (Johns Hopkins Coronavirus Resource Center, 2020). These figures, in particular the number of infections, represent only the number of individuals that have been tested. One of the particularities of SARS-CoV-2 is that asymptomatic individuals, which appear to represent 80% or more of all infected, are still contagious. This obviously dramatically complicates the task of tracking the disease as a large fraction of infections will most likely go undetected as people do not present any or only mild symptoms.
Recently, we have shown that sewage monitoring, i.e. the analysis of SARS-CoV-2 RNA in the influent of wastewater treatment plants (WWTPs), can be a sensitive tool to control the circulation of SARS-CoV-2 in society (Medema et al., 2020). Since its first application, sewage monitoring has been adopted by an increasing number of organisations around the world. The aim of this project is to develop and implement a sensitive tool to monitor the early circulation of SARS-CoV-2 in the population by analysing critical locations in the urban water cycle as a proxy for the prevalence of COVID-19.
The focus for the critical locations in this project was in South Africa and the Netherlands. Sampling included wastewater treatment plants and large water bodies etc.
By testing and implementing this solution in South Africa and the Netherlands, we can compare how sewage data can support public health authorities in their monitoring and response to the pandemic. In addition, we have developed and implemented advanced data visualization and analysis tools that will enable us to collect and interpret sewage and epidemiological data.
Our interdisciplinary research project contributes to a better understanding of virus transmission and exposure, with a focus on the human-environment interface. This has direct consequences for the prevention and control of infections. Furthermore, the impact of measures to contain the spread of the virus can be evaluated (first research priority of the New Global Research and Innovation Forum on the Coronavirus of 2019: towards a research roadmap; WHO, March 2020).
Before the onset of the SARS-CoV-2 epidemic in the Netherlands, 7 waste water treatment plants were selected, which serviced a number of cities, also Schiphol, the main airport in the Netherlands. Waste water was tested using RT-PCR against three fragments of the nucleocapsid protein gene (N1-3) and one fragment of the envelope protein gene (E).
On 6 February, 3 weeks before the first case was reported, 27 February, no SARS-CoV-2 was detected. On 5 March, the N1 fragment was detected on 5 of 7 locations, although total numbers of infections were still very low. In one particular catchment, viral RNA could be detected in wastewater days before the first case was reported in official figures. These findings clearly indicate that waste water can be used as a very sensitive and early warning indicator for SARS-CoV-2.
In the northern hemisphere, countries, including the Netherlands, are slowly relaxing current measures put in place to mitigate the circulation of the virus. However, there are substantiated fears that there might be a second wave of infections which could have even more devastating consequences for health and the economy. Because widespread testing of individuals remains a challenge, it is important to pursue surveillance efforts to make sure that decreasing trends, but most importantly, resurgence of the virus in communities can be monitored efficiently and inform decision making.
Preliminary results obtained with sewage surveillance prove that the approach can help monitor, understand and, most importantly, help detect at an early stage the resurgence of the virus. For this purpose, the Netherlands consortium envisages implementing and further developing the methodology in The Netherlands to inform the government and health authorities about virus circulation in communities.
This project is a continuation of these endeavours to monitor and forecast the spread of the illness known as Covid-19.
On the other side of the world, the situation on the African continent is becoming more and more serious. In particular, South Africa has been facing a sharp increase in the number of registered infections, although once again the total number of infections is likely much higher. As in The Netherlands, having efficient monitoring strategies is of the utmost importance to mitigate the spread of the infection. However, in communities with poorly functioning wastewater treatment plants, or in communities lacking any formal sewerage networks, such as is the case in many regions of South Africa, this is more complicated; raw sewage or poorly treated sewage enters rivers. We monitor these water bodies in this study too.
The likelihood of detecting viral particles, whether infectious or not in river systems is therefore very high. It is therefore proposed that, in addition to sampling of wastewater treatment works, South Africa’s rivers also be sampled at defined points, particularly where known non-point sources of sewage contamination are occurring as a result of unsewered informal housing communities. Greywater polluted by sewage in unsewered communities can also be sampled as a potential epidemiological indicator.