Airflow Determines Natural Airborne Transmission of Tuberculosis in a Guinea Pig Model

ABSTRACT Tuberculosis (TB) is transmitted through the air, yet the determinants of natural airborne transmission remain poorly defined. Early twentieth-century guinea pig studies demonstrated efficient airborne transmission of Mycobacterium tuberculosis (Mtb), but this paradigm has not been reestablished in contemporary containment facilities. Here, we show that ventilation can impose airflow constraints that suppress transmission under otherwise permissive conditions. Using a guinea pig model of animal-to-animal exposure, we combined transmission experiments with quantitative airflow measurements and particle transport modeling to explain why some housing configurations fail to support effective exposure. Static environments and excessive unidirectional airflow prevented transmission, whereas controlled low-velocity airflow restored evidence of exposure, including tuberculin skin test conversion, antigen-specific immune responses, and pulmonary inflammation consistent with early infection. These findings identify airflow as a critical constraint on airborne TB transmission and provide a reproducible framework to dissect host, microbial, and environmental determinants of spread. Competing Interest Statement The authors have declared no competing interest. Footnotes Computational fluid dynamics modeling has been added to the manuscript, thereby introducing two new figures (Figures 5 and 6) and 6 supplemental movies. The supplemental methods have also been updated to include details on computational modeling.