Seamless numerical analysis of transient infectious droplet dispersion and inhalation exposure - In silico study

Abstract

To address the problem of airborne transmission caused by droplets/droplet nuclei containing infectious viruses such as influenza A, tuberculosis, and SARS-CoV-2, the transmission dynamics of infectious droplets in indoor environments, from the generation/emission from an infected subject to the exposure of the target subject via indoor air, must be comprehended seamlessly and accurately. Research on indoor airborne transmission requires rigorous prior ethical review, and experimental studies on humans (in vivo and/or in vitro) are severely limited. Therefore, research methods based on in silico models; i.e., numerical modeling and analysis approaches, are preferred, owing to their flexibility for case and sensitivity analyses. In this study, assuming airborne transmission of SARS-CoV-2 in an indoor environment, we develop and perform a seamless and continuous numerical analysis of infectious droplet dispersion from a coughing infected subject and the subsequent inhalation exposure of a target subject (via the respiratory tract) through transient breathing. We focus on the effects of respiration patterns, particle-size changes due to evaporation, and indoor physical distance between the subjects, on the exposure concentration and distribution of inhaled droplets in the respiratory tract. The results show that, when an infected person coughs within a physical distance of 1 m, inhalation exposure results in significant differences in the inhalation–exhalation timing of breathing, and local environmental conditions have a dominant effect on the inhalation exposure. In short-range airborne transmission, the particle-size change due to evaporation has a dominant effect on the estimation of the inhalation exposure concentration in the respiratory tract.