• Derek J Bays, Minh-Vu H Nguyen, Stuart H Cohen, Sarah Waldman, Carla S Martin, George R Thompson, Christian Sandrock, Joel Tourtellotte, Janelle Vu Pugashetti, Chinh Phan, Hien H Nguyen, Gregory Y Warner, and Bennett H Penn.
• Division of Infectious Diseases, Department of Internal Medicine, University of California Davis Medical Center, Sacramento, California.
• Infect Control Hosp Epidemiol. 2021 Sep 1; 42 (9): 1046-1052.

ObjectiveTo describe the pattern of transmission of severe acute respiratory coronavirus virus 2 (SARS-CoV-2) during 2 nosocomial outbreaks of coronavirus disease 2019 (COVID-19) with regard to the possibility of airborne transmission.DesignContact investigations with active case finding were used to assess the pattern of spread from 2 COVID-19 index patients.SettingA community hospital and university medical center in the United States, in February and March, 2020, early in the COVID-19 pandemic.PatientsTwo index patients and 421 exposed healthcare workers.MethodsExposed healthcare workers (HCWs) were identified by analyzing the electronic medical record (EMR) and conducting active case finding in combination with structured interviews. Healthcare coworkers (HCWs) were tested for COVID-19 by obtaining oropharyngeal/nasopharyngeal specimens, and RT-PCR testing was used to detect SARS-CoV-2.ResultsTwo separate index patients were admitted in February and March 2020, without initial suspicion for COVID-19 and without contact or droplet precautions in place; both patients underwent several aerosol-generating procedures in this context. In total, 421 HCWs were exposed in total, and the results of the case contact investigations identified 8 secondary infections in HCWs. In all 8 cases, the HCWs had close contact with the index patients without sufficient personal protective equipment. Importantly, despite multiple aerosol-generating procedures, there was no evidence of airborne transmission.ConclusionThese observations suggest that, at least in a healthcare setting, most SARS-CoV-2 transmission is likely to take place during close contact with infected patients through respiratory droplets, rather than by long-distance airborne transmission.

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