Surface and air contamination with SARS-CoV-2 from hospitalized COVID-19 patients in Toronto, Canada

Kotwa, J. D.; Jamal, A. J.; Mbareche, H.; Yip, L.; Aftanas, P.; Barati, S.; Bell, N. G.; Bryce, E.; Coomes, E. D.; Crowl, G.; Duchaine, C.; Faheem, A.; Farooqi, L.; Hiebert, R.; Katz, K.; Khan, S.; Kozak, R.; Li, A. X.; Mistry, H. P.; Mozafarihashjin, M.; Nasir, J. A.; Nirmalarajah, K.; Panousis, E.; Paterson, A.; Plenderleith, S.; Powis, J.; Prost, K.; Schryer, R.; Taylor, M.; Veillette, M.; Wong, T.; Zhong, X. Z.; McArthur, A. G.; McGeer, A. J.; Mubareka, S.

Background The aim of this prospective cohort study was to determine the burden of SARS-CoV-2 in air and on surfaces in rooms of patients hospitalized with COVID-19, and to identify patient characteristics associated with SARS-CoV-2 environmental contamination. Methods Nasopharyngeal swabs, surface, and air samples were collected from the rooms of 78 inpatients with COVID-19 at six acute care hospitals in Toronto from March to May 2020. Samples were tested for SARS-CoV-2 viral RNA and cultured to determine potential infectivity. Whole viral genomes were sequenced from nasopharyngeal and surface samples. Association between patient factors and detection of SARS-CoV-2 RNA in surface samples were investigated using a mixed-effects logistic regression model. Findings SARS-CoV-2 RNA was detected from surfaces (125/474 samples; 42/78 patients) and air (3/146 samples; 3/45 patients) in COVID-19 patient rooms; 14% (6/42) of surface samples from three patients yielded viable virus. Viral sequences from nasopharyngeal and surface samples clustered by patient. Multivariable analysis indicated hypoxia at admission, a PCR-positive nasopharyngeal swab with a cycle threshold of [≤]30 on or after surface sampling date, higher Charlson co-morbidity score, and shorter time from onset of illness to sample date were significantly associated with detection of SARS-CoV-2 RNA in surface samples. Interpretation The infrequent recovery of infectious SARS-CoV-2 virus from the environment suggests that the risk to healthcare workers from air and near-patient surfaces in acute care hospital wards is likely limited. Surface contamination was greater when patients were earlier in their course of illness and in those with hypoxia, multiple co-morbidities, and higher SARS-CoV-2 RNA concentration in NP swabs. Our results suggest that, while early detection and isolation of COVID-19 patients is important, air and surfaces may pose limited risk a few days after admission to acute care hospitals.