Genomic surveillance of wastewater can be an early warning system to predict Covid-19 outbreak and to identify new virus variants, according to a study.
The study conducted by researchers from Tata Institute for Genetics and Society (TIGS), National Centre for Biological Sciences (NCBS) and Biome Environmental Trust has shown that genomic surveillance of wastewater can effectively be used to understand Covid-19 trends and for early detection of new viral emergents.
The study was conducted in Bengaluru, a release from TIGS said.
Wastewater samples were collected once every week from 28 sewer sites across the city, between January 2022 and June 2022. Positive samples for SARS-CoV-2 were analysed using RT-qPCR, a demonstrated economical surveillance tool used globally to trace the spread of Covid-19, it said.
The findings of this study divulge real time genomic surveillance of wastewater as a key tool to understand the emerging patterns of virus populations and of new virus variants in densely populated areas.
The scientists compared the viral load of SARS-CoV-2 virus in both wastewater samples and clinical samples obtained from individuals affected by Covid-19 infections and found them to be positively correlated with each other.
This confirms genomic surveillance of wastewater to be a complementary tool to gain insights on SARS-CoV-2 virus populations in a community, according to the release.
Genomic sequencing is the backbone of wastewater surveillance and needs to be done in real time to understand the variants that cause the emerging viral load patterns in wastewater, said Dr Farah Ishtiaq, scientist heading the wastewater surveillance at TIGS.
According to the research, wastewater was also found to have higher number of virus variants in it than found in clinical samples.
The emergence of new variants in wastewater is indicative of a significant number of individuals in the community to have been already infected by new viral strains. Many new variants were observed at different intervals of time along the duration of the study. However, these variant types and their time of detection were consistent across all sampling sites in the city.
Wastewater surveillance should be used as a complementary surveillance approach to identify disease hotspots said Dr Uma Ramakrishnan, Professor, NCBS.
The outcomes of the sensitivity analysis suggest that the total number of individuals infected with SARSCoV-2 virus in Bengaluru was four times higher than the number obtained via clinical tests, the release added.
This information was shared with the city's municipality (Bruhat Bengaluru Mahanagara Palike and Bangalore Water Supply and Sewerage Board) officials, to help them take informed decisions when strategising plans to curtail the spread of Covid-19.
Based on the findings of this study, clinical testing for Covid-19 was increased in some locations in Bengaluru. The scientists believe the insights gained from this study will significantly improve public health surveillance, both for the ongoing Covid-19 pandemic and also other infections which may adversely affect in the future.
Current surveillance and infrastructure are being scaled beyond SARS-CoV-2, to other pathogens (e.g. dengue, malaria). This will also help understand major pathways and drivers of antimicrobial resistance in the environment said Rakesh Mishra, Director, TIGS.
