Detailed Exploration into the Underlying Physicochemical Properties of Aerosol that Govern How Long SARS-CoV-2 Remains Infectious in the Aerosol Phase
ALLEN E. HADDRELL, Mara Otero-Fernandez, Henry Oswin, Tristan Cogan, Jamie Mann, Thomas Hilditch, Jianghan Tian, Daniel Hardy, Darryl Hill, Adam Finn, Andrew Davidson, Jonathan P. Reid,
University of Bristol Abstract Number: 156
Working Group: Aerosol Science of Infectious Diseases: What We Have Learned and Still Need to Know about Transmission, Prevention, and the One Health Concept
AbstractThe COVID-19 pandemic has exposed the need for an improvement in our understanding of the transmission of respiratory pathogens, the shortcomings in which have manifested in the prolonged debate surrounding likelihood of the transmission of SARS-CoV-2 being airborne (1).
A detailed understanding of the airborne decay of the virus, and how this is affected by environmental parameters such as relative humidity, temperature, air content and aerosol composition, will provide the necessary insights into the relative risk of different environments and the potential impact of measures such as social distancing, masks and ventilation on public health. These insights may also allow the implementation of new and more effective infection control strategies such as indoor environmental (e.g. humidity, temperature, HNO3, CO2) controls.
To be presented are the outcomes of study, in which a novel approach was used to study the underlying mechanisms by which SARS-CoV-2 virus is inactivated in the aerosol phase. This approach involves the coupling together of two single particle analysis instruments:
1) Comparative kinetic electrodynamic balance (CK-EDB) – Measures the physicochemical properties of individual droplets, including evaporation rate, phase change, pH, hygroscopic growth curve, etc.
2) Controlled electrodynamic levitation and extraction of a bioaerosol onto a substrate (CELEBS) – Measures the loss of viral infectivity in the aerosol phase as a function of time (in this study, from 5 seconds to >40 minutes), environmental conditions (relative humidity, temperature, [CO2(g)], [HNO3(g)]), and droplet composition (artificial saliva, MEM, [NaCl]). In this study, the delta variant of SARS-CoV-2 was probed.
Through combining these techniques, we have coupled together the changes in the physicochemical properties of the aerosol phase with viral infectivity. This is done in the same conditions and (uniquely) on the same time scale. Making these measurements on the same time scale is unique to this approach and is essential if these complex relationships are to be accurately interpreted. The results of this study have afforded detailed mechanistic insights into the loss of viral infectivity in the aerosol phase. Specifically, it will be presented that aerosol pH (alkaline) and aerosol phase are the primary drivers of loss of infectivity in the aerosol phase.
[1] Mandavilli, A. (2021) 239 Experts With One Big Claim: The Coronavirus Is Airborne. The New York Times.
[2] Oswin, H.; Haddrell, A.; Otero-Fernandez, M.; Mann, J.; Cogan, T.; Hilditch, T.; Tian, J.; Hardy, D.; Hill, D.; Finn, A.; Davidson, A. Reid, J. (2022). The Dynamics of SARS-CoV-2 Infectivity with Changes in Aerosol Microenvironment. Pre-print, doi.org/10.1101/2022.01.08.22268944.