Risk factors of nosocomial COVID-19 at Grenoble Alpes university hospital

Introduction: During the COVID-19 pandemic, hospitals implemented infection prevention strategies to reduce nosocomial transmission. Nevertheless, these strategies sometimes failed and determination of risk factors of transmission is crucial. Objectives: Our main objective was to determine the risk factors of nosocomial Covid-19 at Grenoble Alpes University hospital (CHUGA). Methods: A case-control study was conducted at CHUGA. A retrospective data collection was performed between 01/09/2020 and 31/01/2021. Adults patients hospitalized in medicine or surgery units were included. Infants or patients hospitalized in ICU were excluded. Case patients were patients with a nosocomial Covid-19 (clinical symptoms and positive PCR for SARS-CoV-2 or positive PCR for SARSCoV- 2 ≤ 28CT);control patients were patients without infection (negative PCR for SARS-CoV-2). They were matched by their length of stay and their period of admission. Bivariate and multivariate analysis were performed with a conditional logistic regression by Stata 12.0. Results: A total of 1393 patients with Covid-19 were hospitalized;722 patients were included in the case-control analysis ( ncase = 281;ncontrol = 441). In bivariate analysis, case patients were significantly older (OR:1.25;CI95% [1.12;1.40]), had more often a roommate (OR:1.74;CI95% [1.23;2.43]), more often a co-infection (OR:1.73;CI95% [1.26;2.36]), more often a severity risk factor of Covid-19 (OR:2.06;CI95% [1.14;3.71]) and a higher Charlson comorbidity index (OR:1,09;CI95% [1,01;1,20] than control patients. In an adjusted model that included the admission in the emergency room and the existence of a severity risk factor, the risk factors of nosocomial Covid-19 were: older age (aOR:1.24 per 10 years;CI95% [1.08;4.41]), having a roommate (aOR:1.63;CI95% [1.14;2.33]), and having a co-infection (aOR:1.62;CI95% [1.17;2.26]). Conclusion: Older patients with co-infection hospitalized in a multiple room were more susceptible to nosocomial Covid-19. These preliminary results need to be consolidated taking into account exposition to contagious healthcare workers or contagious patients.