In France, wastewater monitoring, as a tool for assessing the health of the population, is carried out under the SUM’EAU program (Microbiological Monitoring of Wastewater). It was launched under the auspices of the Ministry of Health and the Ministry of Ecology, with scientific support from Santé publique France for the epidemiological surveillance component and from the National Agency for Food, Environmental and Occupational Health & Safety (ANSES) for the analytical component. In 2023, this program contributed to monitoring the circulation of the SARS-CoV-2 virus based on 12 wastewater treatment plants (WWTPs): Dijon, Grenoble, Lille, Marseille, Nancy, Orléans, Paris, Pau, Rennes, Rouen, and Toulouse. In 2024, the system was expanded to include monitoring at 54 WWTPs to improve the spatial resolution of viral circulation tracking.

Extending wastewater surveillance to other pathogens also offers a promising avenue for complementing current surveillance systems for other infections—which rely on individual data—such as respiratory viral infections that cause seasonal epidemics (influenza, bronchiolitis).

Objectives of wastewater surveillance

• Detect the presence or absence of the virus (currently SARS-CoV-2)

• Track trends in viral circulation

• Contribute to the evaluation of the effectiveness of public health interventions

This surveillance is part of a comprehensive, long-term approach and aims to complement other surveillance systems already in place (community healthcare, long-term care facilities, hospitals). It enables the detection and tracking of disease spread within a population and can be conducted independently of screening strategies and practices. The primary objective is to detect early warning signs that may emerge, such as the presence of the SARS-CoV-2 genome or an acceleration in the circulation of the virus within a given population.

What is wastewater and how does it work?

Wastewater is water that has been contaminated by domestic and/or industrial use. It can be divided into two types:

• domestic wastewater, including:

  • household water (resulting from its use for personal hygiene, laundry, dishwashing, and floor cleaning),

  • toilet water (water used to flush toilets and consequently contaminated with feces and urine);

• non-domestic wastewater (runoff from rainwater, industrial sources, etc.).

In the case of public sewer systems, wastewater is conveyed via sewers (combined or separate, depending on whether or not rainwater is conveyed together) to a wastewater treatment plant (WWTP) where it is treated before being discharged into the environment.

Wastewater contains a range of physical, chemical, and biological contaminants of human, environmental, and/or industrial origin, linked to the activities and practices of groups of people and/or facilities, as well as to their health status. In particular, certain viruses can be detected in the feces of infected individuals, which makes it possible to monitor wastewater to detect, and even quantify, the presence of certain pathogens. This is particularly the case for the SARS-CoV-2 virus, which causes COVID-19.

How is the monitoring conducted?

A weekly sample is collected at one of the wastewater treatment plants (WWTPs) in the SUM’EAU network, selected based on population and territorial representativeness criteria. Each sample is then sent to one of the four laboratories selected through a competitive bidding process: Eaux de Paris (Ile-de-France), IAGE (Auvergne-Rhône-Alpes, Paca-Corse, Occitanie, Nouvelle-Aquitaine), Inovalis (Pays-de-la-Loire, Centre-Val-de-Loire, Brittany, Normandy), Eurofins (Hauts-de-France, Grand-Est, Burgundy-Franche-Comté). These laboratories perform microbiological analyses to detect the presence of the virus (currently only SARS-CoV-2) and quantify it. The results are then transmitted to Santé publique France for the production and reporting of indicators used to estimate the circulation of the virus across the country and track trends.

How are the results reported?

Surveillance data are published in the national weekly bulletin on acute respiratory infections, as well as as open data on data.gouv.fr.

A system that is part of a European initiative

Wastewater surveillance is a discipline currently being developed in most Member States under the impetus of the European Commission. Santé publique France participates in the EU-WISH (Wastewater Integrated Surveillance for Public Health in Europe) project, an initiative involving 26 countries and 61 partners that aims to improve wastewater surveillance for public health across Europe.