A New Approach for Respiratory Droplet Trajectory: Implications for Viral and Bacterial Disease Transmission in Emergency Departments.

Background: The objective of this study is to devise a simplified approach for estimating respiratory particle trajectory to avoid infection in gathering places of emergency departments.

Methods: To the authors' knowledge, no sufficient/obvious data exist on lateral routes of disease transmission through respiratory droplets along the x-axis. The present study establishes a preliminary baseline approach based on the upper pharynx-mouth geometry for lateral social distancing to protect susceptible persons from the droplets of an infected person. An enhanced version of ART (Aydin's Research Team) model has been employed as a supplementary tool of Stokes's law for quantification of motion dynamics of the virus/bacterium-laden droplets in public indoor places.

Results: A range of droplet diameters varying from 1 μm to 2000 μm were considered in this study. The droplets with a diameter of ≤ 22.5 μm can completely evaporate during settling and droplet nuclei can remain in the air for extended periods. An individual Influenza virus can stay airborne for 34.4 days, while a single Streptococcus bacterium remains suspended for 18.6 hours. The proper social distancing between infected and healthy persons should be about 2.9 and 0.9 m longitudinally, and 0.45 and 0.15 m laterally based on the novel aspects of the present study for sneezing/coughing and breathing/talking, respectively. The trajectory of respiratory particles in the streamwise and radial directions resembles the shape of a truncated cone due to the upper pharynx-mouth relationship.

Conclusion: The outcomes of this study can help further understanding of respiratory particle trajectory, thereby improving measures to mitigate disease transmission.