A decision-making tool to help fight the pandemic
Xavier Litrico, Group Chief Research & Science Officer at SUEZ, speaks about Covid-19 City Watch
Provided with these early indicators of change in the circulation of the virus within a given area, local public and health authorities are able to:
- Monitor high-risk or critical facilities (care homes, hospitals and clinics, and buildings with a high occupancy rate);
- Implement early preventive measures (screening tests, awareness campaigns for protective measures such as face coverings, etc.);
- Limit access to certain sensitive facilities.
A flexible solution for epidemic outbreaks
SUEZ offers a flexible solution that can adapt to changing circumstances:
- A foundation with moderate surveillance, comprising a research element, which helps define the sampling strategy for different levels of surveillance, sampling and analysis at wastewater treatment plants and key sensitive sites for a set period decided in consultation with the local authority. The results of the analysis are viewed on a special platform and SUEZ provides a guide to interpreting the data.
- Depending on how the epidemic evolves, optional modules can be added to this foundation. Strong or maximum surveillance modules have higher and more widespread sampling and analysis rates.
SUEZ launches COVID-19 City Watch
Credit: SUEZ group
A six-stage approach
- Collection of sewer system data, to identify and map impact zones, for example high wastewater output, river basins, etc.
- Identification of sensitive areas: care homes and community health centres, schools, buildings with a high occupancy rate, recreational areas, etc.
- Sectorisation of the sewer system: network data is used to compartmentalise districts and sub-districts to help locate potential clusters.
- Sampling: automatic samplers take samples continuously over 24 hours to provide an average daily count.
Samples are taken every week to ensure reliable results.
- Sample analysis: SUEZ laboratories analyse the samples using a protocol developed in conjunction with the OBEPINE network which involves identifying and quantifying the genetic markers of the SARS-CoV-2 virus responsible for COVID-19. Wastewater samples are first pre-concentrated then the RT-qPCR (Reverse Transcription quantitative Polymerase Chain Reaction) technique is used to detect and quantify SARS-CoV-2 RNA. At the same time, a special RT-qPCR analysis of F-specific RNA bacteriophages is also carried out to avoid a dry/rainy weather variation bias in municipal wastewater.
- Visualisation of results on a dynamic map and data interpretation.
Outside of an epidemic, the appearance of a high concentration at a point in the network can signify the formation of a cluster. In this case, surveillance points can be increased to identify the epidemic cluster.
Generally speaking, trend analysis can identify areas in which the epidemic risk is either increasing or decreasing.
Health experts at SUEZ provide help in interpreting the data.
Modular levels of surveillance
- Absence of an epidemic signal and/or presence of a “background” indicator: MODERATE surveillance through sampling:
- at wastewater treatment plant inflow
- at sensitive sites (care homes, community health centres, schools, etc.)
- Detection of a growing quantity of viral markers at wastewater treatment plant inflow or at sensitive sites: switch to MAXIMUM surveillance
- Increase in number of samples
- Sampling of district collectors
- Focus on the infected district(s)
- Stabilisation or decrease in the concentration of viral markers in wastewater: switch to HIGH surveillance
- Reduction in number of samples
- Stop focus on the infected district(s)
- Continue sampling of district collectors
- End of epidemic: switch to MODERATE surveillance
- Reduction in number of samples
- Stop sampling of district collectors
The number and location of sample points for each option are decided in consultation with local authority services during the sectorisation study.
The options are decided in consultation with the local authority, depending on how the epidemic evolves.