Numerical modeling of airborne transmission from airway mucosa of infected person to that of uninfected individual via indoor airflow

To elucidate the mechanism of airborne transmission caused by virus-laden droplets/droplet nuclei, such as SARS-CoV-2, it is essential to clarify the transmission dynamics of infectious particles in indoor environments, from the respiratory tract of an infected person to that of an uninfected individual. In this study, assuming airborne transmission of SARS-CoV-2 in an indoor environment, we developed and conducted a seamless numerical analysis of (i) the size distribution of droplets/droplet nuclei using the Discrete Phase Eulerian Wall Film (DP-EWF) model, (ii) exhalation of droplets/droplet nuclei using the Computational Fluid and Particle Dynamics (CFPD) method, (iii) subsequent inhalation exposure of an uninfected person (via the respiratory tract), and (iv) time-series and heterogeneous changes in viral load (RNA copies/mL in mucus) in the respiratory tract predicted by a host cell dynamics (HCD) model that captures viral infection within the respiratory system. This comprehensive set of numerical analyses can accurately reproduce changes in viral load in droplets/droplet nuclei as a function of elapsed time since the onset of infection. Such insights contribute to a more accurate assessment of the risk of airborne infection in indoor environments.