Sewers or sewage treatment plants can provide near real-time outbreak data as they constantly collect human fluids shed by infected population. Real-time community sewage detection can be taken as early as possible to restrict the movement of the local population, working to minimise the pathogen spread and threat to public health
The ongoing global pandemic of coronavirus disease 2019, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been declared as a public health emergency of international concern (WHO, 2020).
Several research studies across the globe have confirmed that SARS-CoV-2 ribonucleic acid (RNA) has been detected in faeces of not only symptomatic but also asymptomatic patients. It has also been seen that sewers or sewage treatment plants (STPs) can provide near-real-time outbreak data because they constantly collect human fluids shed by infected population.
Thus, wastewater-based epidemiology (WBE) is a promising approach to understand the prevalence of viruses in any given wastewater treatment plant (WWTP) catchment population.
A densely populated country like India will require constant vigilance to contain Covid-19 infection hot spots, unless and until either a vaccine is proven to be effective or herd immunity is achieved, to combat the spread of SARS-CoV-2. Real-time community sewage detection can be taken as early as possible to restrict the movement of the local population, working to minimise the pathogen spread and threat to public health.
This could help the timely determination of whether there are Covid-19 carriers (both asymptomatic and symptomatic) in an area to enable preventive measures such as rapid screening and quarantine, even before the residents of that city have been tested.
In India, the pandemic steadily rose from April 2020 with peaking in mid-August 2020. The cumulative confirmed cases have significantly lowered at present.
Several research groups across the globe have reported detecting novel coronavirus SARS-CoV-2 in wastewater. In Switzerland, École Polytechnique Fédérale de Lausanne (EPFL) researchers, working in association with the Swiss Federal Institute of Aquatic Science and Technology (EAWAG) on wastewater sampling and analysis developed a study in March 2020, which acts as an early warning signal for spread of SARS-CoV-2 in communities. Similarly, in April 2020, sewage sampling across greater Paris (France) for more than one month, researchers have detected a rise and fall in novel coronavirus concentrations that correspond to the shape of the SARS-CoV-2 outbreak in the region.
Other researchers have also reported detecting novel coronavirus SARS-CoV-2 in wastewater in countries such as: Australia (Ahmed et al, 2020), Cyprus (Michael-Kordatou et al, 2020), Ireland (Cahill et al, 2020), Italy (La Rosa et al, 2020), Japan (Haramoto et al, 2020), South Africa (Street et al., 2020), The Netherlands (Dutch Water Sector, 2020), Spain (Chavarria-Miró et al, 2020), USA (Peccia et al and Hart & Halden et al, 2020), and India (Kumar et al and Arora et al., 2020).
For effective dissemination of knowledge created by the current research efforts, and to empower collaboration on a global scale for wastewater-based epidemiology of SARS-CoV-2, there are various ongoing initiatives such as the European Union’s NORMAN - SCORE Joint Initiative (Sewage Analysis CORe group Europe) (score-cost.eu/), COVID-19 WBE Collaborative (covid19wbec.org/), Biobot Analytics (biobot.io/), NSF Research Coordination Network (RCN) (sites.nd.edu/rcn-wastewater-sarscov2/), COVIDPoops19 (https://twitter.com/COVIDPoops19?s=20), Global Water Pathogen Project (GWPP) (waterpathogens.org/) and others.
In IIT Gandhinagar, India, Kumar et al, 2020, for the first time, detected the presence of three SARS-CoV-2 genes (ORF1ab, N and S virus) in wastewater. The samples were collected in May 2020 from Old Pirana WWTP in Ahmedabad (Gujarat) to understand the application of WBE surveillance in India.
The WWTP has a capacity of 106 MLD receiving effluents of Civil Hospital treating Covid-19 patients. The number of gene copies was found comparable to that reported in the untreated wastewaters of Australia, China, and Turkey and lower than that of the USA, France, and Spain. A similar study was conducted by researchers of Dr B Lal Institute of Biotechnology (Rajasthan) with samples from hospital wastewater as well as from WWTPs of Jaipur, which has been a pandemic hotspot (red zone) since April 2020.
To analyse the presence of SARS-CoV-2 in the community wastewater of different catchments in Chennai city in India, a group of scientists led by Chakraborty et.al from SRM Institute of Science and Technology, Mu Gamma Consultants Pvt Ltd (MGC) and The Energy and Resources Institute (TERI) jointly implemented an intensive wastewater surveillance study, the first-of-its-kind in the southern region of India.
The study entailed partial lockdown and post lockdown survey along the wastewater discharge points in Adayar and Cooum Riverine belt flowing through the densely populated region of Chennai to develop an early signalling spread of Covid-19 in communities during partial and post-lockdown periods in 2020. This study gave interesting insights for informing policy actions.
The wastewater surveillance study in Chennai has the potential for replication in other Indian cities like Delhi as well as upscaling it for larger geographic areas covering a large population. Also, it could potentially be one of the bases for scientifically informed decisions to implement public health intervention strategies consistent with legal and ethical considerations in India.
At present, Delhi has 41 Sewage Treatment Plants (STPs) with a cumulative treatment capacity of 3,149 MLD. Out of 41 STPs, 32 STPs (2,775 MLD) are operational and 9 STPs (373 MLD) are non-operational . Also, importantly, 75 per cent of pollution is contributed by three major drains (Najafgarh, Supplementary and Shahdara) out of all the drains falling into the river Yamuna. Given the current sewage management scenario of Delhi, a wastewater surveillance study (similar to the one conducted by SRM IST, MGC and TERI in Chennai) can be taken up in the national
Capital to track the SARS-CoV-2 virus in the wastewater samples from major drains falling into the Yamuna river and select STPs.
The advantages of wastewater surveillance in Delhi will include the monitoring of wastewater samples from sewage treatment plants and major drains of the Yamuna river in Delhi can help in estimating the number of infected individuals, and hence provide robust scientific evidence for informed decision making at the policy level.
This is an early, cost-effective, unbiased community-level indicator of the presence of Covid-19 and of “hot-spots” within a community. It will support risk mitigation decisions for the communities, and guide decisions about where and when to impose or relax more targeted restrictions on movement and activity. It will help alert asymptomatic infections in the community through real-time community sewage detection could be determined.
It will be very useful for positioning resources and triggering public actions for improved health outcomes. It will also alert second and subsequent waves, and develop preparedness towards outbreak of other pandemics in the future.
To track any resurgence of Covid-19, national wastewater surveillance programmes are being implemented in various countries like the USA, Finland, Germany, the Netherlands, and Pakistan. The same can be planned for India. In the past, WBE has played an important role in the eradication of polio in 2011 in India, and at present, wastewater surveillance continues at 52 WWTPs and unregulated catchment areas for detection of poliovirus.
This surveillance network can be a viable resource for the detection of SARS-CoV-2 in wastewater in the country, including the national Capital Delhi.
There is a need to identify the key issues and challenges related to the development of validated methodological protocols for the quantitative analysis of SARS-CoV-2 in wastewater.
The data generated from the SARS-CoV-2 wastewater monitoring system in Delhi might be used to show a roadmap for tracking disease, intensifying testing, re-introducing public orders related to social distancing or quarantines (if needed), and even lifting restrictions once a cessation of infection is confirmed.
(Paromita Chakraborty is Associate Professor, SRM Institute of Science & Technology, and Girija K Bharat is director, Mu Gamma Consultants Pvt Ltd, Gurugram)
