Exhaled aerosols and saliva droplets measured in time and 3D space: Quantification of pathogens flow rate applied to SARS-CoV-2

Abstract

SARS-CoV-2 and its ever-emerging variants, are spread from host-to-host via expelled respiratory aerosols and saliva droplets. Knowing the number of virions which are exhaled by a person requires precise measurements of the size, count, velocity and trajectory of the virus-laden particles that are ejected directly from the mouth. These measurements are achieved in 3D, at 15000 images/second, and are applied when speaking, yelling, and coughing. In this study 33 events have been analysed by post-processing ~500000 images. Using these data, the flow rate of SARS-CoV-2 virions have been evaluated. At high concentrations, 10^7 virions/mL, it is found that 136 to 231 virions are ejected during a single cough, where the virion flow rate peak is capable of reaching 32 virions within a millisecond. This peak can reach tens of virions/ms when yelling, but reduced to only a few virions/ms when speaking. At medium concentrations, ~10^5 virions/mL, those results are hundreds of times lower. The total number of virions that are ejected when yelling at 110db, instead of speaking at 85db, increases by two to three fold. From the measured data analysed in this article, the flow rate of other diseases such as influenza, tuberculosis or measles, can also be estimated. As these data are openly accessible, they can be used by modellers for the simulation of saliva droplet transport and evaporation, allowing to further advance our understanding of airborne pathogen transmission.

Exhaled aerosols and saliva droplets measured in time and 3D space: Quantification of pathogens flow rate applied to SARS‐CoV‐2

“…All results recorded in this study are free to access in Ref. [44] and can be used by modellers as boundary conditions for their simulations. This will enable significant improvements of numerical simulations for deducing the influence of different external parameters.…”

“…The presented data are openly accessible and free to download, from Ref. [44] providing modellers with a realistic and complete set of input data. The 'Results' section presents the experimental results for individual events related to Subject 1, whereas the data collected for Subjects 2 and 3 are shown in the Supplementary Information.…”