CORONASTEP: Monitoring of SARS-CoV-2 in Luxembourg wastewater

Infection with SARS-CoV-2, the etiological agent of the COVID-19 pandemic, is accompanied by excretion of the virus in the faeces of infected individuals. Thus, the quantification of SARS-CoV-2 in wastewater would enable the prevalence of infections in the population to be monitored by means of wastewater-based epidemiology, particularly where classical routine testing capacity is limited. The overall aim of the CORONASTEP project was to determine to what extent SARS-CoV-2 is present in domestic wastewater, and to what extent wastewater surveillance can be used to monitor and understand the circulation of SARS-CoV-2 at national level. To this end, several scientific questions and technical challenges had to be addressed. We had to assess the significance of the presence of SARS-CoV-2 in wastewater, and understand how faecal shedding parameters (frequency, duration, magnitude) in (a)symptomatic individuals influence the uncertainty and variability of data collected from wastewater treatment plants. Furthermore, given that the infectious risk of wastewater containing SARS-CoV-2 is of crucial importance, we needed to verify the infectious status of viruses at the entrance to the wastewater treatment plant. To achieve these aims, specific methodological objectives were met, such as the establishment and validation of a concentration procedure adapted to enveloped viruses, the implementation of quantitative assays using RT-PCR and RT-ddPCR, the implementation of an infectivity assay using cell culture, and a high-throughput sequencing approach to determine viral strain diversity and the emergence of new variants. Since the beginning of the pandemic period, the data collected during this study have been of great help to policymakers in monitoring the progress or retreat of pandemic waves, and in making decisions on social distancing and quarantine efforts based on SARS-CoV-2 prevalence estimated in wastewater. These data have also generated new scientific insights into the behaviour and persistence of this new coronavirus in the environment. 

Part of this huge work was carried out in collaboration with the Luxembourg Institute of Health (LIH), the “Laboratoire National de Santé” (LNS) and the University of Luxembourg (LCSB). In addition, the wastewater syndicates (SIACH, SIVEC, STEP, SIDERO, SIDEN and SIDEST), the “Ville du Luxembourg”, the Hesperange city as well as the “Administration de la Gestion de l’Eau” (AGE) provided their kind and valuable assistance in collecting samples, acquiring wastewater parameters and gathering demographic data. The Ministry of Health and the Health Inspectorate also made a valuable contribution by providing COVID-19 data at national and regional level.