CoVWWSurv - National surveillance of SARS-CoV-2 and its variants in sewage.

Last updated on 24-5-2022 by Cassandre Dugailliez

In short

It concerns the implementation of a surveillance system for coronavirus (SARS-CoV-2) through the analysis of sewage, the objective being the early detection of any significant evolution of the circulation of the virus in the population. This surveillance system will cover approximately 45% of the Belgian population, by means of the analysis of the sewage entering the wastewater treatment plant, at a rate of two times per week. The sewage analysis focuses on:

  • the viral levels of SARS-CoV-2 (RNA copies/ml)
  • the human faecal contamination load (using a viral indicator: PMMoV), in order to standardise the results on the population covered through the tool (i.e. the people whose stools are tracked by taking sewage samples)
  • at the start of 2022, the surveillance of variants (VoCs) will also be conducted (with European funding), so that their spatio-temporal distribution can be monitored through sewage.

Project summary

The objectives of this surveillance are:

  • the early detection of any significant increase in the circulation of the virus 
  • to monitor the variants
  • to support the decision-makers.

Specifically, the project is useful for:

  • Supplementing and supporting the existing surveillance tools in terms of the early detection of the circulation of SARS-CoV-2. To support decision-making, it is essential that the interpretability of the results from the analysis of sewage is improved. This involves the integration of complementary parameters including:
    • the quantification of SARS-CoV-2 (RNA/ml)
    • a more precise estimation of the number of people included in the sample (through the analysis of faecal contamination indicators)
  • To have more information on the variants circulation and the evolution of their proportion in the population
  • This complements the other surveillance methods in place because: 
    • it reflects the circulation of the virus in asymptomatic people and those with mild symptoms better (than existing surveillance methods)
    • it is independent of the capacity for clinical testing
    • it is non-invasive (no clinical samples required)
    • it is less subject to bias (independent of the current screening strategy)
    • it provides an approach to testing that is fast and good in terms of cost/effectiveness
  • To develop expertise in sewage epidemiology for Belgium, which is useful for monitoring other infectious diseases that are of importance to public health (such as the polio virus in particular) and in the context of detecting potential future epidemics. 

The Epidemiology of infectious diseases service of Sciensano coordinates the project with the involvement of several other services and scientific directorates of the institute: 

  • Service Foodborne Pathogens which coordinates the laboratory and analysis component
  • Service Transversal activities in applied genomics (TAG) for the R&D part of the screening of variants and the development of adapted, sensitive and specific ddPCR methods to variants.

Two types of partnerships are in place, targeting the following objectives respectively:

  • To have a tool that supports the early detection of any resurgence of the COVID-19 epidemic, through the analysis of SARS-CoV-2 in sewage samples. The laboratories involved are: 
    • Sciensano Laboratory (Food-borne pathogens department) for the analyses in Brussels and 50% of the analyses in Flanders
    • E-Biom (a spin-off from UNamur [Univeristy of Namur] and partner of the Société Publique de Gestion de l’Eau — SPGE — the Public Water Management Company) for all of the analyses in Wallonia
    • Laboratorium Microbiologie, Parasitologie en Hygiëne (LMPH — The Microbiology, Parasitology and Hygiene Laboratory) and the Toxicologisch Centrum van de Faculteit Farmaceutische, Biomedische en Diergeneeskundige Wetenschappen of UAntwerpenfor 50% of the analyses in Flanders
  • Improving the surveillance and warning system through more advanced statistical modelling, in order to obtain an increased correlation between the positive clinical cases and the sewage results. The main scientific partners involved in this phase are: UNamur, Ugent, and Sciensano (Epidemiology of Infectious Diseases department).
  • The project also collaborates with the following actors in the sewage sector: Aquafin (Flanders), Hydria (South-Brussels Wastewater Treatment Plant), Aquiris (North-Brussels Wastewater Treatment Plant), in particular for the logistics of sampling and the collection of data that is useful for developing the surveillance (population covered, flow rate of entry to the Wastewater Treatment Plants).

Results

The epidemiological situation based on sewage can be followed weekly via:

  • The “wastewater page“ on Sciensano’s COVID-19 dashboard, which provides a graphical representation of the results “in real time”
  • The weekly report on the latest results, based on a warning system that highlights upward trends
  • The weekly report on the epidemiological situation presented by the RAG (based on multiple indicators) and validated by the RMG, available in French and Dutch
  • A methodology appendix with further details on the methods employed in the surveillance of sewage

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