A mechanics-based model for inhalation-driven transmission of smallpox

This study models human inhalation during normal breathing, replicated through high-fidelity Large Eddy Simulations of 15 and 30 L/min airflow rates. Inhaled transport of pathogenic particulates against the ambient airflow is then monitored using an inert discrete phase model. The anatomically realistic airway geometries used in the simulations are clinically healthy, developed from high-resolution medical scans from two subjects. The results, with cross-disciplinary inputs, can help quantify infection onset parameters in the airway. Smallpox from the Poxviridae family, with infection trigger sites at the oropharynx and in the lower airway, is picked as a sample pathogen capable of airborne transmission. The simulated findings on inhaled transmission to such infective sites are integrated with virological and epidemiological parameters for smallpox, namely the virion concentration in host ejecta material and the typical exposure durations for confirmed infection. This integration helps estimate the infectious dose, or the number of virions sufficient to infect an exposed individual. Our findings also confirm that a precise consideration of vortex-dominated effects on respiratory transport is crucial for a reliable mechanistic model of infection onset.