Monitoring traces of the novel coronavirus SARS-CoV-2 in wastewater is emerging a potential approach to track the circulation of the virus, which can serve as an early-warning tool. In a recent finding, researchers from France investigated the levels of SARS-CoV2 genome in wastewater and found that it correlated well with the number of confirmed fatal cases caused by COVID-19 in Paris.
The preprint of the study, conducted between March 5 and April 7, 2020, was published by medRxiv last week.
Samples from 23 raw and eight treated wastewater samples were collected from three major wastewater treatment plants. A time-course analysis by quantitative RT-PCR technique showed that all raw wastewater samples, and 75 per cent of the treated wastewater samples, tested positive for traces of SARS-CoV-2 virus.
The viral load in the treated wastewater effluents, however, was 100 times less than the viral load in the raw wastewater samples.
The second part of the study compared the level of SARS-CoV2 genomes in wastewater samples with the number of confirmed fatal cases due to COVID-19 over time.
The genome levels in raw wastewater increased from 105 equivalent viral genomes per litre to nearly 107 equivalent viral genomes per litre as the number of fatalities increased in France and Parisian area and crossed nearly 1,000 cases during the study period.
Hence, the study found that the increase of genome units in raw wastewaters accurately followed the increase in the number of fatal cases observed at the regional and national level.
While medRxiv indicated that the findings were yet to be peer-reviewed, the importance of quantitative monitoring of viral genomes in wastewaters for better tracking of the virus at national, regional or local scale is evident.
Our environment is like a sink and at the receiving end of our activities. But it returns us what it takes from us.
Surveillance in the environmental samples such as soil, water, sewage and wastewater can be crucial from the point of view of a long-term containment strategy of a disease or public health issue.
The approach has been previously used to detect the presence of other bacteria and virus in wastewater. Monitoring of antibiotic resistant bacteria, resistance conferring genes or antibiotic residues in sewage or wastewater samples have facilitated the environmental surveillance of antimicrobial resistance (AMR). This has led to a growing understanding of environment as a reservoir of AMR determinants.
Countries such as Australia and the Netherlands have also detected the presence of the virus in wastewater or sewage samples so far.
Following emergence of the virus in China in December 2019, the virus rapidly spread to other countries, eventually causing a global pandemic. Since the virus can be present in stool samples of symptomatic or asymptomatic individuals, it eventually finds a way into sewage and wastewater that can be monitored for timely interventions.