Hospital contact patterns and vulnerability to SARS-CoV-2 outbreaks

The transmission risk of SARS-CoV-2 within hospitals can exceed that in the general community because of more frequent close proximity interactions (CPIs). Heterogeneity of risk across wards is still poorly described. We measured CPIs in 15 clinical wards across three hospitals using wearable sensors over 36 hours in spring 2020. This data was combined with a transmission model to estimate and compare transmission risks across wards. We found a four-fold range of epidemic risk between wards, with patients frequently presenting high risk to patients and healthcare workers (HCWs). Using a simulation study, we then assessed the potential impact on global risk of targeting individuals for prevention based on their contact patterns. We found that targeting individuals with the highest cumulative contact hours was most impactful. This study reveals patterns of interactions between individuals in hospital during a pandemic and opens new routes for research into airborne nosocomial risk. One Sentence Summary We measured contacts between staff, patients and visitors in 15 hospital wards, and used models to predict epidemic risk and evaluate interventions. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement Fondation de France (MODCOV project grant 106059) as part of the alliance framework "Tous unis contre le virus" Universite Paris-Saclay (AAP Covid-19 2020) The French government through its National Research Agency project Nods-Cov-2 ANR-20-COVI-0026-01 and SPHINX ANR-17-CE36-0008-01 ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Comites de Protection des Personnes, Ile de France VI gave ethical approval for this work Commission Nationale de l'Informatique et des Libertes gave ethical approval for this work I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The code used for each analysis is available at , along with a subset of the data.