Context. SARS-CoV-2 wastewater-based epidemiology (WBE) has been advanced as a relevant indicator of distribution of COVID-19 in communities, supporting classical testing and tracing epidemiological approaches.
Gap. Up to now, there are not many studies on a large geographical scale combining several situations and a medium or long term follow-up.
Aim. The objectives of this study were threefold: i) quantify the concentration of SARS-CoV-2 RNA at the inlet of a meaningful number of WWTP spread throughout France, ii) examine whether this monitoring is consistent with prevalence data in order to assess the relevance of WBE for COVID-19 and iii) evaluate the interest of taking into account the context of the sample collection.
Methods. An extensive sampling campaign, including ten municipal wastewater treatment plants, has been conducted in different cities of France over a 20-weeks period, encompassing the second peak of COVID-19 outbreak in France. A well-recognised ultrafiltration - RNA extraction - RT-qPCR protocol was used and qualified, showing 5.5 +/- 0.5% recovery yield on heat-inactivated SARS-CoV-2. Importantly the whole, solid and liquid, fraction of wastewater was used for virus concentration in this study.
Findings. Campaign results showed medium to strong correlation between SARS-CoV-2 WBE data and COVID-19 prevalence. To go further, WWTP inlet flow rate and rain statistical relationships were studied and taken into account for each WWTP in order to calculate contextualized SARS-CoV-2 loads. This metric presented improved correlation strengths with COVID-19 prevalence for WWTP particularly submitted and sensitive to rain.
Utilization. A commercial offer, nammed VigieCovid19, was packaged based on these results. Sampling context is reported in an interactive dashboard, together with raw SARS-CoV-2 WBE results, in order to properly interpret SARS-CoV-2 RNA monitoring in sewers.
