Long-term monitoring of SARS-CoV-2 in wastewater of the Frankfurt metropolitan area in Southern Germany

Agrawal, S.; Orschler, L.; Lackner, S.

Wastewater-based epidemiology (WBE) is a great approach that enables us to comprehensively monitor the community to determine the scale and dynamics of infections in a city, particularly in metropolitan cities with a high population density. Therefore, we monitored the time course of the SARS-CoV-2 RNA concentration in raw sewage in the Frankfurt metropolitan area, the European financial center. To determine the SARS-CoV-2 concentration in sewage, we continuously collected samples from two wastewater treatment plant (WWTP) influents (Niederrad and Sindlingen) serving the Frankfurt metropolitan area and performed RT-qPCR analysis targeting three genes (N gene, S gene, and ORF1ab gene). In August, a resurgence in the SARS-CoV-2 RNA load was observed, reaching 3 x 10^13 copies/day, which represents similar levels compared to April with approx. 2 x 10^14 copies/day. This corresponds to an also continuous increase again in COVID-19 cases in Frankfurt since August, with an average of 28.6 incidences, compared to 28.7 incidences in April. Different temporal dynamics were observed between different sampling points, indicating local dynamics in COVID-19 cases within the Frankfurt metropolitan area. The SARS-CoV-2 load to the WWTP Niederrad ranged from approx. 4 x 10^11 to 1 x 10^15 copies/day, the load to the WWTP Sindlingen from approx. 1 x 10^11 to 2 x 10^14 copies/day, which resulted in a preceding increase in these loading in July ahead of the weekly averaged incidences. The study shows that WBE has the potential as early warning system for SARS-CoV-2 infections and as monitoring system to identify global hotspots of COVID 19.