Scientists of the National Chemical Laboratory (NCL) along with officials of the Pune Municipal Corporation (PMC) have found traces of the SARS-CoV2 virus, which causes Covid-19, in sewage samples collected from different areas in the city. The samples are being collected since December 2020 as part of a pilot project with experts saying testing wastewater could serve as a cost-effective early warning system which could help officials keep track of coronavirus at an early stage, even among asymptomatic persons.
Pune Municipal Commissioner Vikram Kumar told The Indian Express: “Wastewater tracking has been used (even) before the Covid-19 pandemic to monitor for polio. We explored the possibility of using environmental water surveillance to monitor the virus activity and engaged in a small pilot project with NCL for the purpose. The findings have been interesting and we are now waiting for a larger proposal for the institution,” Kumar said.
The civic body has appreciated the work done by scientists at NCL and have recommended that the exercise continue for another year in view of the anticipated third wave. The Pune Knowledge Cluster has sought additional permissions from PMC and also had an MoU with NCL to facilitate the joint efforts.
“We have been able to detect the presence of SARS-CoV2 RNA in sewage samples as part of our pilot study,” Dr Mahesh Dharne, Scientist, Biochemical Sciences Division, CSIR-NCL, and project coordinator, said. An official presentation was made by the scientific team at a meeting chaired by Deputy Chief Minister Ajit Pawar recently and a detailed report will be submitted soon to the PMC.
Besides four Sewage Treatment Plants (STP) that come under the civic body’s purview, a drain that open into a river and another STP plant on NCL campus were selected for the study. Pune-based NGO Ecosan Services Foundation helped in the sampling work.
From December 2020 till date, around 23 wastewater samples from PMC STPs, 17 from open drains entering the river and nine from NCL colony have been processed and assessed for the presence of SARS-CoV-2 nucleic acid by RT-qPCR method.
Sewage samples from the open drain entering the river were also profiled from the period ranging from December 2020 to March 2021 and sequenced by ARTIC V3 protocol on MinION sequencer.
“The idea of Wastewater-Based Epidemiology (WBE) was implemented during the polio pandemic in order to better understand the affected areas and the same is being used to understand the community infection dynamics of SARS-CoV-2. Domestic wastewater with faecal matter containing viral particles/load enters the drainage system (which is why) sewage treatment plants are considered to be hot spots for disease surveillance. The virus is then concentrated from wastewater and monitored through a real-time polymerase chain reaction (RT-PCR) technique, followed by direct meta-sequencing to detect mutations/variants,” Dr Dharne said. Besides Dr Dharne, the NCL team working on the project comprised microbiologist Dr Syed Dastager and chemical engineer Dr Sanjay Kamble.
Karnataka government has introduced a city sewage surveillance system in Bengaluru while CSIR-Centre for Cellular and Molecular Biology (CCMB) scientists are also engaged in similar studies in Hyderabad, Delhi, Kolkata, Chennai, Mumbai, Allahabad and a few cities of Andhra Pradesh. Dr Rakesh Mishra, advisor to CSIR-CCMB, said that samples are flown to the National Environmental Engineering Research Institute (NEERI) at Nagpur where the data is analysed.
“There is a lot of potential in this environmental wastewater surveillance,” Dr Mishra said.
He pointed out the wide-spread transmission of SARS-CoV 2 can make testing every individual a challenging task in densely populated countries.
In their recent study in Hyderabad, CCMB scientists estimated the total number of individuals exposed to SARS-CoV2 based on the detected viral gene copies per litre and viral particle shedding per individual to suggest that sewage-based surveillance can be an effective approach to study the infection dynamics, which can help in the efficient management of the SARS-CoV2 spread.