This paper presents a review of the current research outcomes and needs regarding SARS-CoV-2 in wastewater. The fact that such a review should exist so soon after the presence of this virus in wastewater became an issue of interest seems remarkable. But it is also a clear reflection of the avalanche of research on this topic, which is still only in its first few rumblings.
The authors of this paper include researchers with long and distinguished careers in developing the science around viruses in water and wastewater (Charles Gerba, Annalaura Carducci and Joan Rose), teamed with some younger scientists all now right at the forefront of this field internationally (Masaaki Kitajima, Warish Ahmed, Kerry Hamilton, Eiji Haramoto and Kyle Bibby). So this review and its conclusions can be considered to be very well informed.
The review does provide an update and guidance on “wastewater-based epidemiology” from the presence of SARS-CoV-2 genetic material (RNA) in sewage. This topic has also been covered fairly extensively on this blog (select “wastewater-based epidemiology” from the “Tags” at the bottom of any of our blog pages to find examples).
More unique about this review is the effort to pull together the key information that will be required for assessing public health risks associated with the presence of viable SARS-CoV-2 virus in wastewater and drinking water.
These include attention to the survival and inactivation of coronaviruses and enveloped surrogate viruses in water and wastewater matrices. The authors also describe the data needs (and data availability) for quantitative microbial risk assessment (QMRA) for COVID-19. These include the need for dose-response data for SARS-CoV-2, for which they identify none as currently available (and maybe SARS-CoV might be the currently best available surrogate).
While the paper did include a passing mention of the important WHO metric “Disability Adjusted Life Years” (DALYs), the authors did not identify the establishment of a “DALYs-per-case” value for COVID-19 as among the current knowledge gaps and research needs. Nonetheless, such a value will be required in order to establish safe levels of drinking water management by current WHO (and Australian) procedures. It will also be neccesary to develop a quantitative understanding of the performance of various water treatment processes for removing or inactivating the virus.
The concluding remarks from this review include a call for more information and understanding to be developed as a matter of urgency:
“Our understanding on the potential role of wastewater in SARS–CoV-2 transmission is largely limited by knowledge gaps in its occurrence and survival in wastewater and environmental waters and removal by wastewater treatment processes. There is an urgent need for collecting these pieces of information to understand and mitigate the human health risks associated with exposure to wastewater and environmental waters potentially contaminated with SARS-CoV-2”.
M. Kitajima, W. Ahmed, K. Bibby, et al., SARS-CoV-2 in wastewater: State of the knowledge and research needs, Science of the Total Environment (2020).