Simulating Near-field Enhancement in Airborne Transmission with a Quadrature-based Model

LAURA FIERCE, Alison Robey, Cathrine Hamilton, Pacific Northwest National Laboratory

     Abstract Number: 460
     Working Group: Aerosol Science of Infectious Diseases: What We Have Learned and Still Need to Know about Transmission, Prevention, and the One Health Concept

Abstract
Airborne pathogens are transmitted when pathogen-laden respiratory particles are expelled from an infectious person, deposit to the respiratory system of a susceptible person, and cause infection. Some respiratory particles are small enough to remain suspended and contribute to long-range airborne transmission, but exposure to infectious particles is greater in the expiratory jet of an infectious person than in a well-mixed indoor space. Processes governing short-range airborne transmission depend on many parameters that are inherently variable and often poorly constrained, such as the pathogen loading in expelled particles, their variation with respect to size, and the risk of infection in the new host for a given pathogen dose, but uncertainty in model parameters is not easily explored with existing techniques. Some of the most advanced mechanistic modeling studies have used Monte Carlo approaches, but these techniques are computationally expensive, which limits the number of simulations that can be performed. Here we introduce the Quadrature-based model of Respiratory Aerosol and Droplets as an efficient framework for representing short-range and long-range airborne transmission within indoor spaces. We characterized short-range enhancements in airborne exposure across thousands of model scenarios, evaluated the impact of different combinations of controls, and identified the factors that drive variability in the modeled risk of infection across the ensemble of scenarios. We show that exposure to airborne pathogens is enhanced by orders of magnitude during close interactions with an infectious person relative to exposure in a well-mixed room. The horizontal extent of short-range enhancements in airborne transmission extends beyond the travel distance of large droplets.