Investigation of healthcare-associated outbreaks of SARS-CoV-2

The aim of this project is to gain a better understanding of the transmission dynamics of SARS-CoV-2 in healthcare-associated outbreaks, in particular the role of healthcare workers. We will combine epidemiological and genetic data to reconstruct transmission trees.

  • Background

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    During the COVID-19 pandemic, three healthcare-associated (known as nosocomial) outbreaks occurred in distinct sites of the Geneva University Hospitals. After improvements in infection prevention and control, the outbreaks were successfully controlled. Protection of healthcare workers (HCWs) is a key priority whilst caring for SARS-CoV-2 patients. Similarly, preventing healthcare-associated COVID-19 among COVID-19 negative patients is key. Particular attention should be paid to vulnerable patients in long-term care facilities and geriatrics.

  • Research aims

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    The main objective of this study is to reconstruct the outbreaks, combining epidemiological with genetic data, in order to understand transmission dynamics and improve infection control practices and consider additional preventive strategies. Specific aims include:

  • Establish viral transmission pathways of the outbreak and reconstruct a transmission tree
  • Identify the direction of transmission, for example from HCW to HCW, from HCW to patient, from patient to HCW, or from community to HCW.
  • Expected results and envisaged products

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    This is a retrospective cohort study of COVID-19 clusters involving 104 patients and 185 HCWs in three distinct hospital sites of the Geneva University Hospitals. We will obtain clinical and epidemiological data for all SARS-CoV-2 positive patients and HCWs involved in these nosocomial outbreaks. We will construct epidemic curves by ward for patients and HCWs, and compute attack rates and doubling times. These data will be used to construct a putative transmission tree. Genetic sequencing data will provide greater resolution and identify specific clusters and imported cases that could not have been determined by epidemiological analysis alone.

  • Specific contribution to tackle the current pandemic

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    Analysing these nosocomial outbreaks will provide key insights into transmission dynamics of SARS-CoV-2 in the healthcare setting and will inform infection prevention guidelines and control guidelines in successive waves of the pandemic in order to enhance protection of HCWs and patients. Furthermore, this study will demonstrate the added value of genome sequencing in elucidating the complex connectivity of SARS-CoV-2 dissemination in hospitals. Insights from the epidemiological investigations have led to the development of an e-learning tool to improve preventive practices of HCWs in high-risk areas.

  • Original title

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    Combined epidemiological and molecular investigation of 3 nosocomial outbreaks of SARS-CoV-2 cross-infection