Virus stocks were prepared in Vero E6 cells and sequence confirmed by PCR and/or Sanger sequencing. Plaque assays were performed in Vero E6 cells. A manuscript is in preparation with a more detailed description of virus propagation and plaque assays (Klimstra, W., Duprex, P.).
Aerosol exposures were conducted using the Automated Bioaerosol Exposure System (ABES) or AeroMP (Biaera Technologies, Hagerstown, MD, USA) exposure management platform inside a Class III biologic safety cabinet operated under negative pressure. The 3-jet (C3), 6-jet Collison (C6), or Aerogen Solo (AS) nebulizers were used for generation of aerosols.
Aerosol sampling was performed with an all-glass impinger (AGI)-4 (Ace Glass, Vineland, NJ, USA) or SKC Biosampler (SKC Inc, Eighty Four, PA, USA). Aerosol particle size was determined using an Aerodynamic Particle Sizer solely or with the addition of a diluter (TSi, Shoreview, MN, USA).
Extracted nucleic acid samples were tested for SARS-CoV-2 by RT-qPCR following a previously published assay (1) . Two RT-qPCR monoplexes targeting the N and ORF1b were 