As many people would have observed, there is currently a large amount of work being undertaken internationally in support of wastewater-based epidemiology for COVID-19. That is, searching for fragments of genetic material (RNA) from the virus SARS-CoV-2 in sewage (or sludge from sewage treatment plants), with the aim of understanding patterns of infection within communities.
We listed and provided links to nine recent papers on our previous post, here. Reading through these studies, it is clear that there are currently some very big methodological variations among them. For example, there are major variations in sample collection, RNA concentration and extraction, which fragments of RNA to target, quality control procedures, and how to quantitatively interpret the results.
This variability may be helpful in that it means that many diverse approaches are being trialled, which may lead to identification of the optimum approaches. But it also means that it is practically impossible to directly compare the reported results between different cities due to the number of potentially confounding factors that need to be considered.
So it is timely that we begin to see some key papers identifying the need for a more coordinated way forward. This paper, led by researchers at Water Research Australia (WaterRA) provides an important step in that direction.
As each new pre-print reporting wastewater-based epidemiology of COVID-19 is produced, it is accompanied by a flurry of excitement, both in conventional media and on social media. However, the authors of this paper remind us that there is still some way to go with developing the true usefulness of these techniques:
“Currently, there is limited quantitative data on the intensity and duration of shedding of the SARS-CoV-2 virus in faeces and respiratory fluids over the course of infection, and there is no simple way to equate a measure of virions/L of wastewater to the number of infected people in the wastewater catchment from which the wastewater is collected. Therefore, it is important to appreciate that it is uncertain how useful such testing will be in providing information to those tasked with managing the COVID-19 pandemic response”.
Nonetheless, progress is being made and the authors report some major efforts underway to improve coordination and networks among key researchers and other organisations. These include networks in Australia (through Water Research Australia), Canada (Canadian Water Network) and the US/globally (Water Research Foundation).
Beyond the many technical issues requiring further development, the authors describe how there are also important communication challenges requiring attention. These include explaining and communicating that there is no evidence that infectious SARS-CoV-2 virus is transmitted through wastewater. Another need is communicating the costs, value and benefits of environmental surveillance to agencies leading the COVID-19 control strategies. That means communicating the differences and alignments between clinical and environmental surveillance and how the two are complementary.
Hill, K., Zamyadi, A., Deere, D., Vanrolleghem, P. A. and Crosbie, N. (2020) SARS-CoV-2 known and unknowns, implications for the water sector and wastewater-based epidemiology to support national responses worldwide: early review of global experiences with the COVID-19 pandemic. Water Quality Research Journal.