This study on large gatherings was initiated in 2021 by the Santé publique France team in Île-de-France and focused on all the risks associated with large gatherings of any kind. This literature review was shared with partners and health authorities in early 2022 to support risk mapping in preparation for the Paris 2024 Olympic and Paralympic Games. It was updated in 2023 in cooperation with the Infectious Diseases Directorate of Santé publique France to focus on infectious risks during major summer sporting events. The goal was to better identify the challenges posed by the 2024 Olympic Games.

This comprehensive review confirms that cases of infectious diseases are, of course, reported during major summer sporting events. Why wouldn’t they be, since they occur every summer even in the absence of such gatherings: outbreaks of foodborne illnesses, viral infections, Legionnaires’ disease, meningitis, and now* a few locally acquired cases of arboviral diseases (dengue, Chikungunya). However, this review also confirms that no epidemic that was already established prior to these events occurred. This was notably the case for Zika during the 2016 Olympic and Paralympic Games in Rio, meningitis and measles during the 2010 FIFA World Cup in South Africa, and COVID-19 during the UEFA European Championship in the United Kingdom and Italy in 2020. In summary, cases do occur during major summer sporting events, but they do not pose a significant additional public health risk to athletes, spectators, or the general population. This is especially true in cities, such as Paris, which welcome millions of tourists each year.

The published review focused solely on infectious risks capable of causing epidemics. Important point: spectators are present in stadiums and within the Games’ perimeter for relatively short periods of time—shorter, in particular, than the incubation periods of most pathogens. These participants therefore do not have time to contribute significantly to the spread of pathogens or to the risk of an epidemic in a given area and time frame. It is therefore advisable to prepare for the usual summer infectious risks mentioned above, even though the increased number of visitors may pose challenges in terms of management by the Regional Health Agencies (ARS) and interpretation of indicators by Santé publique France. Hence the importance of documenting as precisely as possible the number of people present in real time at a given location and site. Telephone data, for example, which is already used in France for modeling purposes, could be collected for this purpose. Having access to this detailed data will then provide a more accurate estimate of the number of people present (so-called population denominators) when evaluating data or risks.

Other health risks worth mentioning, identified during the initial 2021 review (unpublished), include those observed during heat peaks or prolonged heat episodes, and especially during heat waves. This was observed during the 1996 Atlanta Olympics and the 2021 Tokyo Olympics. These phenomena, which are becoming increasingly frequent in summer even in our latitudes, can have a rapid and massive impact on athletes, participants, and the general population.
It should be noted that the Heat Wave and Health Alert System (SACS), established in France after the summer of 2023 across the entire metropolitan territory and coordinated by Santé publique France in collaboration with Météo-France, is activated between June 1 and September 30. Its objective is to measure the health impact of heat on the population and to provide decision-making support to authorities.

Santé publique France has many years of experience managing large gatherings (Turin 2006, the 2014 D-Day celebrations, COP21 in 2015 in the Île-de-France region, the Grande Armada in 2023, etc.). This experience will continue to grow and must be guided by epidemiological imperatives. Together with all our colleagues at Santé publique France, we were able to conduct a trial run during the 2023 Rugby World Cup and test certain indicators** during the Grande Armada in Rouen.
The key lesson from monitoring these recent large gatherings—which requires significant mobilization of teams—is the importance of anticipating staffing needs. Indeed, this mobilization is in addition to the specific mobilization required for each individual’s other agency assignments.
France has many professionals involved in health surveillance, whether through dedicated surveillance efforts or routine surveillance, such as the Sursaud® syndromic surveillance system, mandatory disease reporting (DO), or reports of unusual health signals. The Paris 2024 Olympic Games provided an opportunity to implement new surveillance systems, such as the use of data from the Paris Fire Brigade (BSPP) or first-aid organizations around the stadiums, in connection with Paris 2024. Surveillance (via the BSPP) enables the collection of reasons for assistance requests and the number of victims treated (in Paris and departments 92, 93, and 94). Data from these surveillance efforts are published weekly throughout the 2024 Olympic Games in the Île-de-France 2024 Olympic Games bulletin. The performance of these new systems must still be evaluated before deciding whether or not to continue using them. Santé publique France, which coordinates the wastewater microbiological surveillance system (SUM’EAU), recently conducted a study aimed at identifying pathogens of interest for surveillance in wastewater in preparation for the 2024 Olympic Games. (See Box – The Value of Wastewater Surveillance During Large Gatherings).

The other lesson from public health surveillance during large gatherings is the inevitable occurrence of a small number of cases that do not pose a public health burden but are nonetheless reported. Regardless of the context, these cases must be investigated and either ruled out or confirmed to determine whether a health risk exists, a process that takes some time.