Experimental aerosol survival of SARS-CoV-2 in artificial saliva and tissue culture media at medium and high humidity

Abstract

SARS-CoV-2, the causative agent of the COVID-19 pandemic, may be transmitted via airborne droplets or contact with surfaces onto which droplets have deposited. In this study, the ability of SARS-CoV-2 to survive in the dark, at two different relative humidity values and within artificial saliva, a clinically relevant matrix, was investigated. SARS-CoV-2 was found to be stable, in the dark, in a dynamic small particle aerosol under the four experimental conditions we tested and viable virus could still be detected after 90 minutes. The decay rate and half-life was determined and decay rates ranged from 0.4 to 2.27 % per minute and the half lives ranged from 30 to 177 minutes for the different conditions. This information can be used for advice and modelling and potential mitigation strategies.

Keywords: SARS-CoV-2; aerosol; coronavirus; humidity; saliva; survival.

Figure 1.

Survival of SARS-CoV-2 in a dynamic aerosol over time under different conditions. Left: SARS-CoV-2 was aerosolised in tissue culture media, TCM (squares) or artificial saliva (circles) and held in a Goldberg Drum for 90 mins at medium relative humidity, RH (filled shapes) or high RH (open shapes). Impinger samples were taken over time and enumerated by TCID₅₀ assay. Each run was performed in triplicate and each time-point was assayed in triplicate. Counts were adjusted for dilution effect of sampling. Graph shows mean values (+/- SEM) for each condition with a line modelling exponential decay (solid lines for TCM, dashed lines for artificial saliva). Right: The theoretical decay of SARS-CoV-2 in TCM (squares, solid lines) or artificial saliva (circles, dashed lines) at medium RH (filled shapes) or high RH (open shapes) with decay as a percentage of starting amount shown. Horizontal dotted lines at 50% represent half-life and at 10% give an indication of time for starting amount to drop by 90% (1 x Log₁₀).