Predominance of inhalation route in short-range transmission of respiratory viruses: Investigation based on computational fluid dynamics

摘要

During the Coronavirus disease 2019 pandemic, short-range virus transmission has been observed to have a higher risk of causing infection than long-range virus transmission. However, the roles played by the inhalation and large droplet routes cannot be distinguished in practice. A recent analytical study revealed the predominance of short-range inhalation over the large droplet spray route as causes of respiratory infections. In the current study, short-range exposure was analyzed via computational fluid dynamics (CFD) simulations using a discrete phase model. Detailed facial membranes, including eyes, nostrils, and a mouth, were considered. In CFD simulations, there is no need for a spherical approximation of the human head for estimating deposition nor the "anisokinetic aerosol sampling " approximation for estimating inhalation in the analytical model. We considered two scenarios (with two spheres Scenario 1 and two human manikins Scenario 2), source-target distances of 0.2 to 2 m, and droplet diameters of 3 to 1,500 mu m. The overall CFD exposure results agree well with data previously obtained from a simple analytical model. The CFD results confirm the predominance of the short-range inhalation route beyond 0.2 m for expiratory droplets smaller than 50 mu m during talking and coughing. A critical droplet size of 87.5 mu m was found to differentiate droplet behaviors. The number of droplets deposited on the target head exceeded those exposed to facial membranes, which implies a risk of exposure through the immediate surface route over a short range.