Testing sewage water may give clue about Covid-19 circulation: Study
Testing sewage water could give authorities clues about the circulation of Covid-19 in cities, new research has found. Scientists in the Netherlands found the virus circulating in sewage water even when cases of Covid-19 were very low and the outbreak was still in its early stages in Dutch cities.
In another analysis, Chinese scientists have suggested the use of paper-based devices (analytical devices for rapid diagnostics of pathogens. For instance, paper-based testing kits for malaria) to trace these pathogens early on.
In the Dutch study, tests were conducted from sewage water samples three weeks before the first case of Covid-19 tested positive in the Netherlands but no markers were found in wastewater. When the test was conducted again on March 4 and 5, one week after the outbreak began in the country, markers were found in wastewater.
Wastewater treatment plants were selected from two large and three medium sized Dutch cities and an airport to draw samples from which ribonucleic acid (RNA) was extracted and reverse transcription polymerase chain reaction (RT PCR) was conducted.
Scientists, however, clarified that there is no evidence yet that sewage is a transmission mode for SARS-CoV-2. Although SARS-CoV-2 has been detected in a significant proportion of stool samples in earlier studies, just two studies reported finding infectious virus from these samples. This indicates virus doesn’t sustain in sewage water for long possibly due to treatment. Surveillance of sewage water, however, offers the opportunity to check for community prevalence of the disease.
“It is important to collect information about the occurrence and fate of this new virus in sewage to understand if there is no risk to sewage work ers, but also to determine if sewage surveillance could be used to monitor the circulation of SARS-CoV-2 in our communities… sewage surveillance could also serve as early warning of the re-emergence of Covid-19 in cities, much like the sewage surveillance for poliovirus that has been used for this purpose,” authors from the KWR Water Research Institute in the Netherlands said in the studypublished in medRxiv.
Another analysis published in the Environment Science and Technology journal by scientists from the School of Water, Energy and Environment, Cranfield University, and Chinese Academy of Sciences said paper based devices to pick up bio-markers in sewage samples similar to those being used for HIV, Malaria, Zika virus, human papillomavirus, among others, can be useful for tracking Covid-19.
Dr Zhugen Yang, Lecturer at Cranfield Water Science Institute, said: “In the case of asymptomatic infections in the community or when people are not sure whether they are infected or not, real time community sewage detection through paper analytical devices could determine whether there are Covid-19 carriers in an area to enable rapid screening, quarantine and prevention.”
“Sewage surveillance has been done for polio and non-polio viruses in the past. But testing sewage samples is not easy. We need RT-PCR now on a large scale for people. 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,” said Dr Shobha Broor, former head of microbiology at All India Institute of Medical Sciences (AIIMS), Delhi. India is testing at only about 36% of its capacity currently, according to the Indian Council of Medical Research.
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