The aim of this study is to evaluate the prevalence of COVID-19 among the workers of our hospital and the factors that are likely to influence this prevalence. It must be underlined that our hospital is settled in two towns and both hospital sites had different missions regarding the admissions of COVID-19-infected patients.

Since December 2019, the COVID-19 pandemic has widespread from China and put under strong tension the health organizations throughout the world, especially since march 2020 in France.

As a consequence, the French hospitals had to cope with a massive amount of COVID-19 infected patients and, thus, their organisations had to evolve in order to be able to admit more patients in their critical care units.

First studies reported an important level of inter-human contagiousness of the SARS-CoV-2 virus with an "R0" (basic reproduction number) superior to 3, which could lead to a massive contamination of healthcare workers since they are directly in charge of infected patients.

Other studies suggested that the healthcare workers are more likely to be contaminated by the COVID-19 than the rest of the population, which pushed governments and hospital managers to put in place individual and collective measures of protection in order to avoid nosocomial transmissions and also to preserve the health of the hospital staffs in a context of high tension on the hospital work force.

There are today few data about the contamination level among the healthcare workers of general hospitals in France and about the severity of these contaminations. A national study is being conducted but on a macroscopic regional scale. In addition to that, the proportion of asymptomatic SARS-CoV-2 contaminated healthcare workers is not known as well as the origin (hospital or community) of the contaminations.

In June 2020, the French Health Ministry decided to launch a collection of epidemiological data in the French hospitals based on serologic tests. Thanks to this action and with the results of all the RT PCR tests systematically conducted since the beginning of the pandemic when a healthcare worker had COVID-19-like symptoms, the Centre Hospitalier Sud Essonne has decided to conduct an observational study.

The aim of this study is to evaluate the prevalence of COVID-19 among the workers of our hospital and the factors that are likely to influence this prevalence. It must be underlined that our hospital is settled in two towns and both hospital sites had different missions regarding the admissions of COVID-19-infected patients.

Inclusion criteria:

• hospital staff working at the Centre Hospitalier Sud Essonne,
• employed by the Centre Hospitalier Sud Essonne between March, 5th, 2020, and August, 31rst, 2020,
• with the result of an RT PCR test or a serologic test,
• this (these) result(s) must have been/be communicated to the occupational health service of the hospital.

Exclusion criteria:

• interim workers,
• workers in holidays during the entire period of inclusion above,
• opposition to participate in this study.

Adult healthcare workers who are not opposed to participate to the research