Testing not enough, scientists examine sewage to gauge COVID-19 spread

Amid several other ways of tracing people who are infected with the novel coronavirus, scientists, taking a cue from the surveillance performed by other countries, have decided to test wastewater and sewage to get a clear idea of the number of people infected.

Given that most Indians are unlikely to be tested for COVID-19, scientists are referring to the country’s surveillance programme for polio and turning to sewage to get a snapshot of the current and expected tally of coronavirus cases in India.

Manish Kumar of the Indian Institute of Technology in Gandhinagar who is working with an international team of collaborators on the project, feels that wastewater epidemiology is a valuable tool to monitor the spread of the novel coronavirus in communities.

The wastewater-based epidemiology (WBE) global collaboration comprises over 50 institutes and researchers headed by Kyle James Bibby of the University of Notre Dame in the US.

The group is coordinating sampling and analytical protocols as well as data-sharing so that results obtained can be compared on a global scale.

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The numbers in India tell their own story of 1.3 billion people vs 9,02,654 tests till Friday (May 1), according to the Indian Council of Medical Research. Over the last five days, India has been averaging 49,800 tests a day.

The number of tests has almost doubled in the last eight days as five lakh tests conducted between March 23 and April 22 has not been sufficient to gauge the spread of the disease.

“The current testing method is not enough to tell the exact situation of the coronavirus infection in India. Even if the people show symptoms for novel coronavirus, it will take three to 15 days actually to detect it,” Kumar, assistant professor at the Department of Earth Sciences, told PTI.

“That is too late. That’s why we thought about wastewater epidemiology. We thought of using wastewater to check if there is coronavirus genetic material or not,” said Kumar.

He said India’s polio monitoring system, which uses a similar surveillance method, could come handy in the fight against coronavirus.

“Sewage-based epidemiology is an indication of what may be missed by a case- based surveillance. The approach can be employed like polio surveillance in the country,” Gagandeep Kang, executive director of the Translational Health Science and Technology Institute, Faridabad, told PTI.

As per a report in nature.com, to date, researchers have found traces of the novel coronavirus in the Netherlands, the United States, and Sweden. They believe analysing wastewater being discharged from COVID-19 treatment facilities can track the infectious disease which is excreted in urine or faeces.

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According to Masaki Kitajima, a world renowned environmental virologist from Japan’s Hokkaido University, “the presence of genetic material of novel coronavirus provides an opportunity to use wastewater as a surveillance tool for the invasion, prevalence, molecular epidemiology, and potential eradication of the virus in a community”.

“The magnitude of COVID-19 spread is such that it provides us an opportunity for interdisciplinary coordination on a global scale to multiply the impacts of individual efforts. Kumar’s team at IITGN has been a key member in this effort,” Kitajima, lead author of one of the first review papers on novel coronavirus in wastewater, told PTI.

“It is a published fact that if somebody is infected with the novel coronavirus, they will excrete it through their body, in the form of faeces and urine, which in turn can be detected in wastewater,” Kumar added.

“We are not going to detect the live coronavirus in wastewater but their RNA (genetic material in viruses) present in sewage water. This collected sample will then be used in gene sequencing to assess how much genetic material of coronavirus is available,” he said, adding that the results can then be extrapolated for a genetic material estimation of the wastewater and assigned with a probable number of people infected in a given locality or community.

“I have sent the protocol to several institutes in India like in IIT Chennai, IIT Roorkee, IIT Guwahati and JNU Delhi, so we all can do sampling following one protocol,” he noted.

He added that the Gujarat Pollution Control Board (GPCB) and Gujarat State Biotechnology Mission (GSBTM) are providing his team all the cooperation to accomplish the work.

Several preliminary studies have reported the detection of SARS-CoV-2 RNA in wastewater in the early stages of local outbreaks which further supports the relevance of WBE, said WBE head Bibby.

“We can determine the burden of undiagnosed infections at the population level, which is critical to refining estimates of case-fatality rates,” he said.

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According to Keisuke Kuroda from Japan’s Toyama Prefectural University, who is also a part of the collaboration, an accurate prediction of infected population by WBE will naturally involve multiple uncertainties, some of which will be linked with various geographic, climatic, demographic, socio-economic, and environmental conditions.

“I believe that Kumar’s team will certainly provide considerable insights into WBEs global application, Kuroda, who has published several papers on the fate of viruses and pharmaceuticals in urban waters of Japan and Vietnam, told PTI.

In a study published last week in the journal Science of the Total Environment, researchers highlighted the economic advantages of the approach over conventional disease testing and epidemiological surveillance.

“Our results show that exclusive reliance on testing of individuals is too slow, cost-prohibitive and in most places, impractical, given our current testing capacity,” said Rolf Halden, a professor at the Arizona State University (ASU) in the US, who was a part of the research team.

“However, when preceded by population-wide screening of wastewater, the task becomes less daunting and more manageable,” he said.

However, the research indicates that careful calibration must be carried out to ensure the accuracy of data, which is acutely sensitive to key variables, including seasonal temperature, average in-sewer travel time, degradation rates of biomarkers, community demographics and per-person water use.

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.

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Gertjan Medema, a microbiologist at KWR Water Research Institute in Nieuwegein, the Netherlands, told <em>nature.com</em> that “one treatment plant can capture wastewater from more than one million people and monitoring effluents at this scale could provide better estimates for how widespread the coronavirus is than testing, because wastewater surveillance can account for those who have not been tested and have only mild or no symptoms.”

“Health authorities are only seeing the tip of the iceberg,” she added.

Using reverse transcription PCR (RT-qPCR) — a laboratory technique of molecular biology — researchers should be able to detect the novel coronavirus with high sensitivity, Kumar said.

Kumar said he has been contacted by the 2030 Water Resources Group of World Bank and several stakeholders in Maharashtra with whom WBE group and his team are generously sharing the sampling and analytical protocol.

The coronavirus can only be defeated by unity, perseverance and persistent efforts, he said.

Dr Shobha Broor, former head of microbiology at All India Institute of Medical Sciences (AIIMS), Delhi feels that the Centre needs to RT-PCR now on a large scale for people.

“Sewage surveillance has been done for polio and non-polio viruses in the past. But testing sewage samples is not easy. Swabs from sewage in cities can be extracted from the common duct in an area to test it. But I think that would be a post -pandemic response in India. We need testing kits to be available right now. That’s a priority,” she told Hindustan Times.

(With inputs from agencies)