The importance of indoor airflow patterns in spreading airborne disease

Tuberculosis (TB) is a leading cause of infectious disease deaths, claiming over 1 million lives each year. The spread of the disease occurs when an infected individual coughs, sneezes, or exhales, releasing airborne particles that can then be inhaled by others. While scientists know that drug-resistant strains and asymptomatic carriers can worsen the problem, they still lack a complete understanding of how airflow and other environmental factors impact the spread of TB.

The issue is that most studies of infectious disease transmission have focused on population-level assessments or individual immune responses, rather than on the role that airflow and mixing play in transmission within indoor spaces. To address this gap, researchers from MIT and the University of Texas Southwestern Medical Center have combined animal transmission experiments with quantitative particle tracking and flow modeling.

This interdisciplinary approach has allowed them to explore how different indoor environments can either promote or mitigate the spread of respiratory infectious diseases like TB.

The key factor in predicting infectious transmission, according to the researchers, is not simply the total ventilation rate, but rather the local pattern of airflow driven by the room's design. This includes factors such as air leakage, points of air inflow and outflow, and the forces generated by an infected person's breathing. As Lydia Bourouiba, the leader of this research team, explains, "The local airflow patterns turn out to be pivotal."

The team's findings provide compelling evidence of the importance of accounting for airflow inhomogeneity when designing indoor spaces to mitigate airborne transmission. This insight is particularly crucial when building or retrofitting spaces, as well as when conducting airborne transmission studies. The researchers hope that their insights can extend beyond their specific model system and demonstrate the broader importance of fluid physics in building designs to prevent the spread of airborne diseases indoors.

Despite the urgency of this issue, there is still resistance to incorporating airflow in routine infectious disease prevention tools. The researchers emphasize that retrofitting existing infrastructure to improve airflow could be achieved at relatively low cost, but the lack of direct evidence has been a barrier to broader adoption of flow physics as a tool for indoor health. By providing this evidence, the team hopes to help close the "black box" that has long surrounded the transmission of respiratory pathogens.