The spatial and temporal distribution of SARS-CoV-2 from the built environment of COVID-19 patient rooms: A multicentre prospective study

PLOS ONE RESEARCH ARTICLE The spatial and temporal distribution of SARSCoV-2 from the built environment of COVID19 patient rooms: A multicentre prospective study Michael Fralick ID1,2,3*, Madison Burella1,3, Aaron Hinz4, Hebah S. Mejbel4, David S. Guttman5,6, Lydia Xing7, Jason Moggridge ID2, John Lapp1, Alex Wong8, Caroline Nott7, Nicole Harris-Linton2, Rees Kassen4, Derek R. MacFadden7 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 1 Sinai Health System, Division of General Internal Medicine, Toronto, Ontario, Canada, 2 LunenfeldTanenbaum Research Institute, Sinai Health System, Toronto, Ontario, Canada, 3 Sault Area Hospital, Sault Ste. Marie, Ontario, Canada, 4 Department of Biology, University of Ottawa, Ottawa, Ontario, Canada, 5 Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada, 6 Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada, 7 The Ottawa Hospital Research Institute, Ottawa, Ontario, Canada, 8 Department of Biology, Carleton University, Ottawa, Ontario, Canada * OPEN ACCESS Citation: Fralick M, Burella M, Hinz A, Mejbel HS, Guttman DS, Xing L, et al. (2023) The spatial and temporal distribution of SARS-CoV-2 from the built environment of COVID-19 patient rooms: A multicentre prospective study. PLoS ONE 18(3): e0282489. https://doi.org/10.1371/journal. pone.0282489 Editor: Amitava Mukherjee, VIT University, INDIA Abstract Background SARS-CoV-2 can be detected from the built environment (e.g., floors), but it is unknown how the viral burden surrounding an infected patient changes over space and time. Characterizing these data can help advance our understanding and interpretation of surface swabs from the built environment. Received: November 24, 2022 Accepted: February 15, 2023 Published: March 13, 2023 Copyright: © 2023 Fralick et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the manuscript and data are available for sharing and to do so researchers can visit https:// cube-ontario.github.io/. Funding: This study was funded by the Sinai Health Department of Medicine Research Fund and an Operating Grant from CIHR (EGA 179419). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Methods We conducted a prospective study at two hospitals in Ontario, Canada between January 19, 2022 and February 11, 2022. We performed serial floor sampling for SARS-CoV-2 in rooms of patients newly hospitalized with COVID-19 in the past 48 hours. We sampled the floor twice daily until the occupant moved to another room, was discharged, or 96 hours had elapsed. Floor sampling locations included 1 metre (m) from the hospital bed, 2 m from the hospital bed, and at the room’s threshold to the hallway (typically 3 to 5 m from the hospital bed). The samples were analyzed for the presence of SARS-CoV-2 using quantitative reverse transcriptase polymerase chain reaction (RT-qPCR). We calculated the sensitivity of detecting SARS-CoV-2 in a patient with COVID-19, and we evaluated how the percentage of positive swabs and the cycle threshold of the swabs changed over time. We also compared the cycle threshold between the two hospitals. Results Over the 6-week study period we collected 164 floor swabs from the rooms of 13 patients. The overall percentage of swabs positive for SARS-CoV-2 was 93% and the median cycle PLOS ONE | https://doi.org/10.1371/journal.pone.0282489 March 13, 2023 1 / 10 PLOS ONE Competing interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: Michael Fralick is a consultant for ProofDx, a start-up company that has created a point-of-care device for COVID-19 using CRISPR. The spatial and temporal distribution of SARS-CoV-2 from the built environment of COVID-19 patient rooms threshold was 33.4 (interquartile range [IQR]: 30.8, 37.2). On day 0 of swabbing the percentage of swabs positive for SARS-CoV-2 was 88% and the median cycle threshold was 33.6 (IQR: 31.8, 38.2) compared to swabs performed on day 2 or later where the percentage of swabs positive for SARS-CoV-2 was 98% and the cycle threshold was 33.2 (IQR: 30.6, 35.6). We found that viral detection did not change with increasing time (since the first sample collection) over the sampling period, Odds Ratio (OR) 1.65 per day (95% CI 0.68, 4.02; p = 0.27). Similarly, viral detection did not change with increasing distance from the patient’s bed (1 m, 2 m, or 3 m), OR 0.85 per metre (95% CI 0.38, 1.88; p = 0.69). The cycle threshold was lower (i.e., more virus) in The Ottawa Hospital (median quantification cycle [Cq] 30.8) where floors were cleaned once daily compared to the Toronto hospital (median Cq 37.2) where floors were cleaned twice daily. Conclusions We were able to detect SARS-CoV-2 on the floors in rooms of patients with COVID-19. The viral burden did not vary over time or by distance from the patient’s bed. These results suggest floor swabbing for the detection of SARS-CoV-2 in a built environment such as a hospital room is both accurate and robust to variation in sampling location and duration of occupancy. Introduction SARS-CoV-2 primarily spreads via aerosols and droplets, and the degree of aerosolization is related to multiple factors, including ventilation [1–4]. Within the built environment, the floor is the most common location where the virus can be detected [5–9]. Floors likely act as a “sink,” collecting the droplets and aerosols produced by infected individuals when those particles eventually fall to the floor. Our previous research was one of the first studies to identify whether the SARS-CoV-2 virus can be detected from the built environment within a hospital [5]. We conducted a multicentre prospective study at two hospitals in Ottawa, Ontario, Canada in which high touch surfaces (e.g., computer keyboard, door handle, telephone receiver, various equipment) and the floors were swabbed weekly for a total of ten weeks. We were able to recover viral ribonucleic acid (RNA) from these surfaces on wards dedicated to patients with COVID-19, but not on wards where there were no patients with COVID-19. The floor was the most common surface where the virus was detected, and this observation has been replicated in other studies [5, 6, 8]. A limitation of this study was that we did not swab within patient rooms, and instead swabbed only the hallways of wards and other common areas within the hospital. One of the first studies swabbing inside the rooms of patients with COVID-19 was by Zhang et al. [8]. They collected over 2000 environmental swabs on inpatient wards, including in common areas and in the rooms of pa (...truncated)