During the peak of Covid-19 pandemic, scientists at IIT-Gandhinagar had found that increased gene copies of the virus in Ahmedabad's wastewater matched the incidence of the disease in the city. The presence of genetic material of the SARS-CoV-2 virus in wastewater proved that water-based epidemiology (WBE) can be used for real-time surveillance of Covid-19 in the country.
WBE is a promising approach to understand the status of disease outbreak in a certain catchment by monitoring viral load in wastewater.
Studies had reported that the novel coronavirus (SARS-CoV-2) is present in the faeces of infected individuals. Genetic material (RNA) from the virus has been found in sewage entering treatment plants.
Because treatment plants collect wastewater across large regions, measuring the level of RNA in untreated wastewater may provide a valuable insight into the percentage of people infected within a region, the researchers said.
A team of scientists from the Indian Institute of Technology (IIT) in Gandhinagar collaborated with the Gujarat Biotechnology Research Centre (GBRC) and the Gujarat Pollution Control Board (GPCB) to study samples of wastewater collected from the Old Pirana Waste Water Treatment Plant (WWTP) in Ahmedabad. Variants of SARS-CoV-2 genes -- ORF1ab, N and S--were found in the wastewater coming into the treatment plant, said the researchers.
According to the scientists, WBE was an effective tool during outbreaks of other viruses such such as poliovirus and hepatitis A. They also noted that no gene was spotted in the effluent leaving the plant after treatment.
The Ahmedabad study was aimed at helping health authorities and policymakers to formulate or upgrade Covid-19 surveillance to have an explicit picture of the phase of the pandemic.
A previous WBE study had indicated the presence of the coronavirus in Italy in December 2019, way before the first confirmed case in the country.
Developing an advanced surveillance system for environmental samples using biotechnological approaches is the need of the hour. This can help us track real time situations not only for the current pandemic but also for seasonal epidemics, Madhvi Joshi, joint director of GBRC.
According to the researchers, 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 US, France and Spain.
Prosun Bhattacharya of Sweden's KTH Royal Institute of Technology noted that WBE can be unimaginably impactful in the war against Covid-19 with the right information about the catchment and number of people residing in the vicinity,
Estimates based on European and North American data suggest that each person infected with SARS-CoV-2 will excrete millions if not billions of viral genomes into wastewater per day. This translates to between 0.15 and 141.5 million viral genomes per litre of wastewater generated, the researchers said.
While infectivity of SARS-CoV-2 through wastewater has not yet been reported, the virus potentially enters the wastewater stream from patient excretions and thus can be a great tool for pandemic monitoring, the researchers said.
Usingreverse transcriptionPCR (RT-qPCR)--a laboratory technique of molecular biology--researchers should be able to detect the novel coronavirus with high sensitivity, Kumar said.
The findings reported by Kumar and colleagues demonstrate the successful detection of SARS-CoV-2 in wastewater --a highly valuable contribution to global SARS-CoV-2 surveillance research efforts, Kyle Bibby,associate professor and leader of Global Collaboration on WBE, University of Notre Dame in the US, told PTI.
Ryo Honda of Japan's Kanazawa University, who is leading a task force on wastewater surveillance in Japan, said the study is an important step for WBE of Covid-19 in India.
Scope of sewage surveillance
Wastewater surveillance is a well established method of detecting poliovirus and antibiotic-resistant bacteria, as well as the use of illicit and prescription medications. Sewage surveillance could also serve as an early warning of the emergence and re-emergence of Covid-19 in cities, according to Dutch scientists.
According to the report published by the Dutch National Institute for Public Health and the Environment, sewage water surveillance is a good way to monitor if viruses such as SARS-COV-2 are present in the population. "Using molecular methods, the virus that causes Covid-19 was detected in wastewater at Amsterdam Schiphol Airport, in Tilburg and at the wastewater treatment plant in Kaatsheuvel. This plant treats the wastewater from Loon op Zand, the town where the first reported Covid-19 patient in the Netherlands lives," the report said.
It is assumed that the coronavirus is likely to have got there from the faeces of patients with Covid-19. While all coronavirus infected patients may not excrete virus genomes into the sewers, a small percentage of infected people, particularly those who experience diarrhoea as a symptom will have the coronavirus in their gastrointestinal tract.
Although it is unlikely that sewage will become an important route of transmission, the pathogen’s increasing circulation in communities will increase the amount of it flowing into sewer systems, a Bloomberg report cited Gertjan Medema, principal microbiologist at the KWR Water Research Institute in Nieuwegein, as saying. Frequent analyses of sewer samples will help authorities to monitor the circulation of SARS-CoV-2 in our communities. In addition, it will also help a city guard its sewage workers against unmitigated risks . “That could complement current clinical surveillance, which is limited to the Covid-19 patients with the most severe symptoms," Medema and colleagues said in their report.
The Dutch National Institute for Public Health and the Environment has previously found norovirus, antibiotic-resistant bacteria and measles in waste water using the same technique.
“The detection of the virus in sewage, even when the Covid-19 prevalence is low, indicates that sewage surveillance could be a sensitive tool to monitor the circulation of the virus in the population,” they said.
