Staff to staff transmission as a driver of healthcare worker infections with COVID-19

Gordon, C. L.; Trubiano, J. A.; Holmes, N. E.; Chua, K. Y.; Feldman, J.; Young, G.; Sherry, N. L.; Grayson, M. L.; Kwong, J. C.

Objectives: To investigate the COVID-19 infections among staff at our institution and determine the interventions required to prevent subsequent staff infections. Design: Retrospective cohort study Participants and setting: Staff working at a single tertiary referral hospital who returned a positive test result for SARS-CoV-2 between 25 January 2020 and 25 November 2020. Main outcome measures: Source of COVID-19 infection. Results: Of 45 staff who returned a positive test result for SARS-CoV-2, 19 were determined to be acquired at Austin Health. Fifteen (15/19; 79% [95% CI: 54-94%]) of these were identified through contact tracing and testing following exposures to other infected staff and were presumed to be staff-staff transmission, including 10 healthcare workers (HCWs) linked to a single ward that cared for COVID-19 patients. Investigation of the outbreak identified the staff tearoom as the likely location for transmission, with subsequent reduction in HCW infections and resolution of the outbreak following implementation of enhanced control measures in tearoom facilities. No HCW contacts (0/204; 0% [95% CI: 0-2%]) developed COVID-19 infection following exposure to unrecognised patients with COVID-19. Conclusions: Unrecognised infections among staff may be a significant driver of HCW infections in healthcare settings. Control measures should be implemented to prevent acquisition from other staff as well as patient-staff transmission.