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Testing not enough, scientists examine sewage to gauge spread of coronavirus

Scientists are turning to wastewater for an indication of how many people have been infected by the SARS-CoV-2 coronavirus. “Sewage-based epidemiology is an indication of what may be missed by case-based surveillance,” an expert said.

HIGHLIGHTS

  • Currest testing in India not enough to gauge spread: Expert
  • Wastewater offers a surveillance alternative
  • India’s polio monitoring system uses similar method

Given that most Indians are unlikely to be tested for Covid-19, scientists are taking a cue from the country’s surveillance programme for polio and turning to sewage to get a clearer snapshot of how many people are infected with the coronavirus.

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

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. The numbers in India tell their own story – a population of 1.3 billion vs 9,02,654 tests till Friday, 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 have almost doubled in the last eight days — India had conducted just about five lakh tests from March 23 to April 22 — but this is still not enough 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, how about wastewater epidemiology, 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.

OPPORTUNITY

“Sewage-based epidemiology is an indication of what may be missed by case-based surveillance,” Gagandeep Kang, executive director of the Translational Health Science and Technology Institute, Faridabad, told PTI.

Kang agreed that the approach can be employed like polio surveillance in the country. 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.

Kumar explained 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.

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 WBE’s 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.

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.

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