The weekly update provides an overview of the coronavirus outbreak in France. It includes daily metrics as well as metrics that are only available on a weekly basis. This format allows for more in-depth analysis, enabling us to examine and contextualize the various data points, and thus gain a more comprehensive understanding of the ongoing outbreak.

Given that the epidemiological situation has changed completely, the epidemiological update must now address new objectives: understanding how the epidemic is unfolding; monitoring the virus strains circulating in the country; and contributing to the evaluation of the measures implemented to combat the coronavirus.

As a reminder, in Phase 1, the surveillance system aimed to identify all COVID-19 cases in France and those occurring abroad, and to track and monitor contacts in order to prevent secondary transmissions. In Phase 2, the objective was to identify transmission chains as quickly as possible in order to break them and prevent—or at the very least delay—the spread of the virus throughout the country.

We are now in Phase 3, which corresponds to widespread circulation of the virus within the population with a rapid increase in the number of cases, making it no longer possible to ensure a comprehensive and reliable count of cases. The surveillance systems put in place in Phases 1 and 2 are therefore no longer suitable for Phase 3. Surveillance has therefore had to be adapted with the implementation of new indicators.

Surveillance today is “population-based” and relies on several indicators developed in collaboration with numerous partners. The objectives of this surveillance are to describe the epidemic in terms of its temporal and spatial spread, severity, identification of at-risk individuals, and estimation of its impact.

We thus have indicators in outpatient care (or community-based medicine) that allow us to track the trend of the epidemic and estimate the number of cases among the population seeking medical care. To do this, we rely on two data sources: the Sentinelles Network, a network of general practitioners and pediatricians, and SOS Médecins.

This data allows us to track the progression of the epidemic among patients at home who do not require hospitalization.

Doctors in the Sentinelles Network thus record the number of patients who have consulted in person or via telemedicine with clinical signs consistent with a COVID-19 infection. They also collect samples from some of these patients according to a predefined protocol, which allows us to estimate, on a weekly basis, the number of new COVID-19 cases that have consulted a general practitioner. The number of SOS Médecins medical procedures for suspected COVID-19 is also tracked.

In terms of virological surveillance, changes in the positivity rates of SARS-CoV-2 tests conducted in hospitals as well as in private medical laboratories also allow for tracking the spread of the virus.

COVID-19 infections have very serious consequences for older adults. Surveillance has therefore been implemented in senior care facilities (retirement homes and nursing homes) to estimate the number of affected facilities, as well as the number of cases and deaths occurring within these facilities.

We monitor visits to hospital emergency departments for suspected COVID-19 through the Oscour® network (Organization for Coordinated Emergency Surveillance), by day and by age group, as well as the proportion of hospitalizations following these emergency department visits.

In hospitals, we track the number of coronavirus-related hospitalizations, including those in intensive care, with data reported daily by the SI-VIC network (Information System for Victim Monitoring). Furthermore, using data from sentinel intensive care units (194 units participating), we can describe the epidemiological characteristics of COVID-19 cases admitted to intensive care in terms of age, sex, comorbidities, severity, and clinical course.

Finally, mortality is monitored through several sources: COVID-19-specific mortality during hospitalization (SI-VIC surveillance), mortality following admission to intensive care (network of sentinel intensive care units), as well as mortality in long-term care facilities for the elderly. Electronic death certification, which covers 20% of national mortality, allows for the characterization of deceased COVID-19 patients in terms of age, sex, place of death, and comorbidities.

Finally, the analysis of all-cause mortality—that is, regardless of the cause of death—enables, within a few weeks, the identification of potential excess mortality in the French population, taking into account age and geographic region.

The GrippeNet surveillance study, coordinated by the Sentinelles Network, also enables the collection of data from populations who do not use the healthcare system.

Finally, we have established a system of repeated population surveys to assess behaviors, attitudes, and practices regarding COVID-19, as well as the level of concern it generates.

The strengths of the COVID-19 surveillance system established in France lie in the versatility and complementarity of the indicators produced, enabling the monitoring and characterization of patients affected by COVID-19 regardless of where they are treated (in the community, in the hospital, in long-term care facilities) and regardless of the severity of their condition (from people who do not use the healthcare system, patients monitored at home, in intensive care, and up to death). This makes it possible to identify those most at risk for this infection and to obtain an overview of the epidemic.

Control measures (barrier measures, social distancing measures, population lockdown) have been implemented to limit the spread of the virus and mitigate its health consequences. Surveillance indicators will enable us to track the impact of these measures on the progression of the epidemic.

For more information: COVID-19: Surveillance System