A SECOND study in Gujarat, based on surveillance of untreated wastewater at four sewage treatment plants in Gandhinagar, has revealed the local administration can be forewarned by a lead of up to two weeks of an impending spike or decrease in Covid-19 cases by such periodic surveillance.
The study, conducted by researchers at IIT Gandhinagar and Gujarat Biotechnology Research Centre (GBRC) with the aid of Gujarat Pollution Control Board (GPCB) and funded by Kiran C Patel Centre for Sustainable Development at IIT-Gn, explored the correlation between the SARS-CoV-2 genetic load in wastewater and the number of cases at the district level to essentially establish if indeed wastewater surveillance can be an effective early warning tool.
It was the case of the researchers that the detected concentrations of SARS-CoV2 RNA in wastewater would reflect the true prevalence of Covid-19 infection in the sewer catchment, which would include those clinically undiagnosed, compared to the number of clinically reported cases, which only covers the diagnosed patients.
The researchers also said it was the “need of the hour” that the “wastewater surveillance must be included as an integral part of Covid-19 pandemic monitoring which may not only help the authorities to identify the hotspots within a city but can provide up to two weeks of time lead for better tuning the management interventions”.
Published as a preprint on December 28, which remains to be peer-reviewed, the latest study expands the scope of an earlier study conducted in May at Ahmedabad’s Old Pirana Waste Water Treatment Plant (WWTP), wherein the first-ever successful effort in India was made to detect the genetic material of SARS-CoV-2, thus establishing wastewater-based epidemiology (WBE) here.
The Ahmedabad-based study had examined wastewater samples on two dates in May. Until then, wastewater surveillance for Covid-19 had been conducted in select few countries of China, USA, Netherlands, Spain, Israel, Turkey, Italy, France, and Australia. Especially, in the case of the Netherlands, Spain and Italy, wastewater surveillance had detected SARS-CoV-2 genome even before the countries recorded its first official cases.
Lead author of the latest study, Prof Manish Kumar, who is from the discipline of earth sciences at IIT Gandhinagar, told The Indian Express that WBE “RTPCR (of the wastewater samples) amplifies genetic material by a million times, telling us whether the virus is present or not,” thus being a more precise and accurate method of determining infection prevalence.
Kumar added WBE can further help determine the efficacy of vaccines. Giving an example, he says, “For example there is a housing society with 100 flats. Taking an average of three members per flat, this becomes a community of 300 people. With periodic sampling of wastewater, one will know the prevalence of Covid-19.”
Wastewater surveillance, he said, has been adopted as a policy in Hyderabad at present. An Ahmedabad study funded by UNICEF, Gujarat, Kumar added, has been conducted to look at samples across 15 wastewater treatment plant sites and is under review at present. This study has seen a longer lag, with a minimum of two weeks’ early warning with respect to Covid-19 case trend. This may also be considered in tandem with the established incubation period of the infection along with viral shedding until up to seven days since the onset of symptoms.
Madhvi Joshi, scientist at GBRC and a co-author of the paper said that we have encouraging results which we are planning to share with policy makers. The group is hopeful that WBE will be taken up formally by public bodies for monitoring pandemic across state.
The Gandhinagar-based study included samples from four wastewater plants, three of which were from the Gandhinagar city – Sargasan, Basan, and an academic institute — and another from a rural district Jaspur.
Effective tool to gauge disease outbreak
Wastewater-based epidemiology (WBE) is a promising approach to understand the status of disease outbreak in a certain catchment by monitoring viral load in the wastewater, as it contains excrement from both symptomatic and asymptomatic individuals. WBE data can help estimate actual infected population, which may be underestimated by clinical surveillance. The method has proven to be an effective tool during in past outbreaks of other enteric viruses, such as polio-virus, hepatitis A and norovirus. Several researchers have also exemplified that it can also be used as an early warning tool for the disease outbreak in a community and used to inform the efficacy of the current public health interventions
Influent (what flows inside the wastewater plant, the untreated part) was collected from each plant — twice in a week at first, followed by weekly collection for two months — from August to September last year. A total of 43 influent wastewater samples were thus collected in the period from the four plants.
Three target genes were considered and presence of two or all target genes in a specific sample, was considered as ‘positive’ for Covid-19. Forty of the 43 samples were thus detected to be positive. The average presence of the three genes combined indicate the confirmed presence of SARS-CoV-2.
The researchers upon time-based comparison of official, documented cases vis-a-vis percentage change in genome concentration in the samples, found that the two factors were in conjunction on a time scale.
The preprint paper noted, “…The percentage change in genome concentration level on a particular date was in conjunction with the confirmed cases registered 1-2 weeks later on a temporal scale by the regulatory authority based on clinical tests… The results unravel the potential of WBE surveillance of Covid-19 as an early warning tool displayed by the adequate presence of SARS-CoV-2 genetic material in wastewater samples though limited cases were documented and based on the immediate future trends.”
Prof Prosun Bhattacharya with KTH at Sweden further commented that this work is a great proof of the capability of wastewater surveillance of COVID-19 in India, which needs to be immediately scaled up to the province, and catchment scale for improvements in management interventions.
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