Experts from the French national public health agency have developed a model framework to identify priority pathogens for wastewater surveillance (WWS) at the upcoming summer Olympic and Paralympic Games in Paris, expected to draw 16 million visitors from around the world.
Viruses that cause polio and flu topped the list.
The researchers used peer-reviewed publications and expert opinion to identify six target pathogens suitable for WWS at mass gatherings, where it can monitor disease levels and guide public health decisions.
"Wastewater acts as a 'mirror' of population health," the researchers wrote. "Through the analysis of sewage samples, wastewater-based epidemiology (WBE) provides information on substance consumption (licit and illicit drugs, tobacco and alcohol), chemical exposure and the circulation of certain pathogens within a population."
The results were posted today in Eurosurveillance.
Narrowing the possibilities
To identify target pathogens, the researchers used criteria informed by the European Centre for Disease Prevention and Control, the Olympic and Paralympic Games, and the World Health Organization, arriving at 60 pathogens.
They then linked those pathogens to those the Games by France's national public health agency included on a risk map for the event, including notifiable diseases, those associated with foodborne illnesses, acute respiratory infections, emerging infectious diseases, and zoonotic diseases, plus six other infectious diseases considered for WWS.
To be monitored in wastewater, pathogens must be excreted in the urine and/or faeces of infected individuals or introduced into sewage via greywater, i.e. from showers and other hygiene activities.
Next, they narrowed the list based on pathogen analytical feasibility, relevance to the event and pathogen characteristics, and value in guiding public-health decision making (eg, allocation of hospital beds, physical distancing).
"To be monitored in wastewater, pathogens must be excreted in the urine and/or faeces of infected individuals or introduced into sewage via greywater, i.e. from showers and other hygiene activities," the researchers said. "Pathogens must also persist in the environment long enough to be detectable by existing analytical methods."
Pathogens that failed to reach the 70% consensus threshold in questionnaires completed by 32 experts were reevaluated by France public health epidemiologists in charge of the country's national wastewater monitoring system using specific criteria, leaving a list of 25 pathogens of interest.
The team eventually arrived at six target pathogens: the viruses that cause polio, influenza A, influenza B, mpox, COVID-19, and measles.
For example, influenza A and B viruses represent a relevant public health burden, with worldwide distribution and year-round circulation. "Integrating WWS during the 2024 OPG [Olympic and Paralympic Games] could provide valuable insight into the background circulation of influenza A and B viruses in Paris during summer months and facilitate tracking of potential transmission chains of the viruses imported by travellers from the southern hemisphere," the authors wrote.
Mpox was chosen for its propensity to remain undiagnosed. "The social stigma related to the higher incidence of mpox among men who have sex with men (MSM) is believed to contribute to its underdiagnosis," they said. "This trend may be exacerbated among foreign tourists during the OPG."
More work needed for Paris
The researchers noted the benefits of WWS, which became widely known during its deployment in monitoring the COVID-19 pandemic: collection of data regardless of symptomatic or asymptomatic status, freedom from the availability of testing or test-seeking behavior, low cost, early-warning function, passive provision of community-level data, ability to quantify virus and evaluate genetic diversity, and its use to guide public health decision making.
At the time of writing, a wastewater sampling strategy proposal based on the conclusion of this study was under review by the French health authorities.
The framework and information gathered in the process are a starting point for a WWS plan for the Paris games, the authors said, but more work is needed before implementation. WWS would use France's existing wastewater treatment network of 54 plants.
"At the time of writing, a wastewater sampling strategy proposal based on the conclusion of this study was under review by the French health authorities," the researchers wrote. "Upon approval, the next steps will include the selection of operators in charge of sampling and partner laboratories that will perform analyses."
Laboratory methods will need to be developed for the detection and quantification of certain pathogens, methods will also need refinement in terms of time efficiency and cost-effectiveness, and the sampling strategy may need adjustment. "A WWS plan for Paris 2024 OPG would serve as an exploratory tool, providing proof of concept for monitoring measles virus, influenza A virus and influenza B virus in Parisian wastewaters," the authors said.
The Olympics begin on July 26, and the Paralympics start on August 28.
