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COVID-19 has placed a tremendous economic burden on countries worldwide: in addition to unprecedented healthcare costs, diagnostic costs can be a barrier in rapid testing and tracing of positive cases. Sewage surveillance might well prove to be a cost-effective surrogate for community testing. While the current need is for COVID-19 surveillance, sewage surveillance platforms can track other less urgent but equally critical pandemics such as antimicrobial resistance, recreational drug usage, etc.
Sewage-based surveillance for COVID-19 has been described in multiple countries and multiple settings. However, nearly all are based on testing sewage treatment plant inflows and outflows using structured sewage networks and treatment systems. Many resource-limited countries worldwide have open canals, lakes, and other such waste-contaminated water bodies that act as a means of sewage effluent discharge. A sensitive, robust, and economical method of SARS-CoV-2 RNA detection from open waste contaminated water bodies in resource-constrained regions is currently lacking.
This study, funded by Swasti and co-authored by Dr. Angela Chaudhuri, was undertaken with the purpose to detect the viral load in open waste-contaminated water sources to improve community-level surveillance and identification of emerging hotspots to facilitate the use of limited public-health resources such as targeted clinical testing. This pilot study was designed to explore the feasibility of using samples from waste-contaminated open-water bodies to track the SARS-CoV-2 virus in a tropical country like India, based on testing of samples collected from an open canal running through a densely populated area in Bengaluru. This method was intended to detect an early outbreak of COVID-19 infection among the habitants at locations lacking a well-structured sewage network, where the waste and excreta from the surrounding residences are conveyed through open sewage drains and discharged into the local water body. The study indicates the detectability of SARS-CoV-2 viral RNA in samples collected from urban, waste-contaminated open-water bodies despite the possibility of dilution by stormwater. The method is simple and economical and is applicable in the Indian context, characterized by higher population density, heat, humidity, tropical climate, lower resource availability, and variable sanitation facilities. Since a substantial part of the informal settlers rely on community toilets and temporary toilets, such detection gives a comprehensive picture rather than sampling solely from conventional wastewater sources like sewage treatment plants (STPs) and inspection chambers.
The striking observations made in this pilot study further support the potential use of the described method for monitoring waste-contaminated open urban water bodies, uncovered sewage drains and untreated wastewater for early detection of infections in communities. The absence of easy access to modern diagnostic resources provides an early warning system and guides the initialization of early responses to contain the community spread of COVID-19 in settings with limited resources. While the current need is for COVID-19 surveillance, sewage surveillance platforms can be used to track other less urgent but equally critical pandemics such as antimicrobial resistance or unregulated opioid usage in the community.