Viral transmission pathways have profound implications for public safety; thus it is imperative to establish an accurate and complete understanding of viable infectious avenues. Whether SARS-CoV-2 is airborn is currently uncertain. While mounting evidence suggests it could be transmitted via the air in confined spaces, the airborn transmission mode has not yet been demonstrated. Here we show that the quantitative analysis of several reported superspreading events points towards aerosol mediated transmission of SARS-CoV-2. Aerosolized virus emitted by an infected person in an enclosed space will accumulate until virion emission and virion destabilization are balanced, resulting in a steady-state concentration $C_{\infty}$. The timescale to accumulation leads to significantly enhanced exposure when virus-carrying aereosol droplets are inhaled for longer duration co-occupancy. Reported superspreading events are found to trace out a single value of the calculated virion exposure, suggesting a universal minimum infective dose (MID) via aerosol. The MID implied by our analysis is comparable to the measured MIDs for influenza A (H2N2), the virus responsible for the 1957-1958 asian flu pandemic. Our model suggests that the likelihood for aerosol-mediated transmission reduces significantly when there is filtration at a rate exceeding the destabilization rate of aerosolized SARS-CoV-2.
Superspreading events suggest aerosol transmission of SARS-CoV-2 by accumulation in enclosed spaces