Aerodynamic Size Distribution and Rates of SARS-CoV-2 Aerosol Shedding: Omicron BA.4 and BA.5

KRISTEN K. COLEMAN, Petri Kalliomäki, Jianyu Lai, Sheldon Tai, Jennifer German, Filbert Hong, Barbara J. Albert, Yi Esparza, Aditya Kiran Srikakulapu, Maria Schanz, Isabel Sierra Maldonado, Molly Oertel, Naja Fadul, Arantzazu Eiguren-Fernandez, Gregory S. Lewis, Kathleen McPhaul, Donald K. Milton, University of Maryland School of Public Health

     Abstract Number: 235
     Working Group: Aerosol Science of Infectious Diseases: Lessons and Open Questions on Models, Transmission and Mitigation

Abstract
Understanding the aerodynamic size distribution and rate of viral aerosols shed by individuals infected with SARS-CoV-2 variants can help inform the utility of COVID-19 mitigation measures designed to reduce infectious aerosol inhalation. Here, we report the rates of viral aerosol shedding among Omicron BA.4 and BA.5 cases and the aerodynamic size distribution of exhaled breath aerosol particles carrying SARS-CoV-2 RNA. From June 15 through December 15, 2022, we recruited 27 individuals with PCR-confirmed COVID-19 to provide 30-minute breath samples into a Gesundheit-II (G-II) exhaled breath aerosol sampler. Among these individuals, 17 provided an additional exhaled breath sample into the newly designed Biocascade Exhaled Breath Sampler (BEBS). We quantified samples for viral RNA using reverse transcription digital polymerase chain reaction (RT-dPCR) and determined the viral RNA copies collected within two aerosol size fractions (≤5 µm and >5 µm in diameter) from the G-II, and four aerosol size fractions (<1.15 µm, 1.15–3.2 µm, 3.3–8.2 µm, and >8.2 µm) from the BEBS. Individuals with a BA.4 or BA.5 infection shed virus in aerosols at an average rate of 7.5x10³ RNA copies per 30-minute G-II sample, with 78% of the total RNA in aerosols ≤5 µm in diameter. Among the BEBS samples, 10% of the total viral RNA was detected in aerosols <1.15 µm, 43% in 1.15–3.2 µm, 37% in 3.3–8.2 µm, and 10% in the >8.2 µm size fraction. Culture work is pending. Based on viral RNA loads, our results indicate that exhaled aerosols ≤3.2 µm contribute the majority of SARS-CoV-2 inhalation exposure. These data support the use of air cleaners and respirators that reduce inhalation of respirable aerosols as environmental and personal protective controls to mitigate COVID-19 transmission.