High efficacy of layered controls for reducing transmission of airborne pathogens

TL;DR

This study demonstrates that layered controls, especially combining masks, distancing, and ventilation, significantly reduce airborne pathogen transmission, with over 99% median exposure reduction in simulated scenarios.

Contribution

The paper quantifies the combined efficacy of masks, distancing, and ventilation in reducing airborne pathogen exposure using a detailed aerosol model.

Findings

Combining masks and distancing reduces median exposure by over 99%.

Enhanced ventilation further decreases exposure levels.

Layered controls are highly effective for outbreak mitigation.

Abstract

To optimize strategies for curbing the transmission of airborne pathogens, the efficacy of three key controls -- face masks, ventilation, and physical distancing -- must be well understood. In this study we used the Quadrature-based model of Respiratory Aerosol and Droplets to quantify the reduction in exposure to airborne pathogens from various combinations of controls. For each combination of controls, we simulated thousands of scenarios that represent the tremendous variability in factors governing airborne transmission and the efficacy of mitigation strategies. While the efficacy of any individual control was highly variable among scenarios, combining universal mask-wearing with distancing of 1~m or more reduced the median exposure by more than 99\% relative to a close, unmasked conversation, with further reductions if ventilation is also enhanced. The large reductions in exposure to airborne pathogens translated to large reductions in the risk of initial infection in a new host. These findings suggest that layering controls is highly effective for reducing transmission of airborne pathogens and will be critical for curbing outbreaks of novel viruses in the future.