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Simulations of Infection Risk for Indoor Transmission of COVID-19
Gregoire Labat, Haider Allawi, Isaac Flores Espinoza, SHERYL EHRMAN, San Jose State University
Abstract Number: 709
Working Group: Infectious Aerosols in the Age of COVID-19
Abstract
Transmission of COVID-19 occurs via respiratory droplets and aerosols emitted by infected persons which directly make contact with mucous membranes of the susceptible persons, or via droplet contamination of surfaces, which are touched by susceptible persons, who then touch mucous membranes. Airborne transmission is now believed to be a significant route. To estimate risk of indoor transmission via aerosols for unvaccinated individuals, we developed a box model of aerosol generation, removal and exposure, assuming well mixed conditions. Infectious aerosol generation rates (quanta/time) are estimated based upon activity level and quanta emission rates reported in literature, removal rates are estimated based upon ventilation parameters, filtration efficiencies and deposition, and exposure risk is estimated using a modified Wells-Riley approach. The model was evaluated by comparison to case studies of outbreaks reported in the literature: choir practice, cycling class, long distance bus ride, and recreational hockey game. Predictions were reasonably close to the observed attack rate in all cases. Effects of masking of both the infectious and susceptible individuals were estimated, incorporating viral load and mask efficiencies as a function of aerosol/droplet size obtained from literature. Results suggest that while mask wearing does not completely prevent transmission, it significantly reduces it, reinforcing the importance of masks as a non-pharmaceutical intervention.