In this study, researchers measured the short-term aerosol efficiencies of SARS-CoV-2 and compared the efficiencies with two other emerging coronaviruses, SARS-CoV (emerged in 2002) and Middle Eastern respiratory syndrome CoV (MERS-CoV; emerged starting in 2012).
The study also quantified the long-term persistence of SARS-CoV-2 and its ability to maintain infectivity when suspended in aerosols (in this specific test environment) for up to 16 hours.
Comparative efficiency experiments were performed across four separate aerobiology laboratories (Tulane University, the National Institutes of Health Integrated Research Facility, the United States Army Medical Institute for Infectious Diseases, and the University of Pittsburgh). The aerosol size distributions produced by the generators used, in mass median aerodynamic diameter (MMAD), ranged from 1-3 µm with a geometric heterodispersity ranging from ≈1.2-1.4.
The comparison of short-term aerosol efficiencies of three emergent coronaviruses showed SARS-CoV-2 is on par with or exceeding the efficiency estimates of SARS-CoV and MERS-CoV. Some efficiency determinations for SARS-CoV-2 ranged to -5.5log10, a full log difference compared to MERS-CoV. The fact that higher efficiencies trended across independent laboratories strengthens this observation. These data suggest that SARS-CoV-2 generally maintains infectivity when airborne over short distances, in contrast to either comparator betacoronavirus.
Results of the aerosol suspension experiments suggest that SARS-CoV-2 is persistent over longer periods of time than would be expected when generated as a highly respirable particle (2 µm MMAD). This is remarkable, as there would be an expected decay and loss in the infectious fraction of airborne virus based on prior susceptibility studies with other relatively environmentally hardy viruses like Monkeypox.
Collectively, this preliminary dataset on the aerosol efficiency and persistence of SARSCoV-2 suggest that this virus is remarkably resilient in aerosol form, even when aged for over 12 hours, and reinforces the conclusions reached in earlier studies of aerosol.
This work was supported by the National Institute of Allergy and Infectious Diseases, National Institutes of Health, and the Office of the Chancellor at the University of Pittsburgh. Work performed at Tulane National Primate Research Center (CJR, ACF) was supported in part by the NIH. RFG was supported by the National Institutes of Health. UTMB work was supported by NIH grant R24AI120942. The Defense Health Program provided the funding for SARS-CoV-2 work at USAMRIID. The work at NIH-IRF was funded in part through the NIAID, Division of Intramural Research and Division of Clinical Research, Battelle Memorial Institute’s prime contract with NIAID under HHSN272200700016I and in whole or in part with Federal funds from the NIAID, NIH, DHHS, HHSN272201800013C. JKB performed this work as an employee of Battelle Memorial Institute. MGL performed this work as an employee of Lovelace Respiratory Research Institute and Laulima Government Solutions, LLC.
Comparative dynamic aerosol efficiencies of three emergent coronaviruses and the unusual persistence of SARS-CoV-2 in aerosol suspensions. 18 April 2020.
