Purpose: During the COVID-19 pandemic, the health care workers (HCWs) at the frontline have been largely exposed to infected patients, running an high risk of being infected by the SARS-CoV-2 virus. This study investigates the epidemiological, clinical and lifestyles characteristics that might play roles in the susceptibility of HCWs to COVID-19 in a hit Italian hospital. Methods:Demographic, lifestyle, work-related and comorbidities data of 1447 HCWs which underwent a nasopharyngeal swab for SARS-CoV-2 were retrospectively collected. For the 164 HCWs positive for SARS-CoV-2, data about safety in the workplace, symptoms and clinical course of COVID-19 were also collected. Cumulative incidence of SARS-CoV-2 infection was estimated. Risk factors for SARS-CoV-2 infection were assessed using a multivariable Poisson regression. Results: The cumulative incidence of SARS-CoV-2 infection among the screened HCWs was 11.33 (9.72-13.21). Working in a COVID-19 ward, being a former smoker (vs being a person who never smoked) and BMI were positively associated with SARS-CoV-2 infection, whereas being a current smoker was negatively associated with this variable. Conclusions: Assuming an equal accessibility and proper use of PPE of all the HCWs of our Hospital, the great and more prolonged contact with COVID-19 patients remains the crucial risk factor for SARS-CoV-2. Therefore, increased and particular care needs to be focused specifically on the most exposed HCWs groups, which should be safeguarded. Furthermore, in order to limit the risk of asymptomatic spread of SARS-CoV-2 infection, the HCWs mild symptoms of COVID-19 should be considered when evaluating the potential benefits of universal staff testing