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

Tuberculosis (TB) spreads through the air when Mycobacterium tuberculosis (Mtb) passes from infected to susceptible hosts, yet the environmental, biophysical and microbial factors governing this process remain poorly understood. In the early twentieth century, Perla and Lurie used guinea pigs to demonstrate natural airborne transmission of Mtb, but such studies have not been revisited in the modern biosafety era. Here, we developed an aerodynamically-optimized guinea pig housing system that models natural, airborne, animal-to-animal Mtb transmission under biosafety level 3 (BSL-3) containment. Iterative engineering and particle transport experiments revealed that airflow is a critical determinant of transmission efficiency. Static housing and excessive unidirectional ventilation both eliminated transmission, whereas controlled, low-velocity airflow enabled aerosol particle retention and exposure of naïve animals. Under these optimized conditions, recipient guinea pigs converted their tuberculin skin tests above a defined positive threshold, developed Mtb-specific antibody responses, and exhibited pulmonary inflammation consistent with infection. These findings demonstrate that flow rates govern natural transmission of Mtb and provide a reproducible small-animal model for studying bacterial, host, and environmental factors that drive infectious spread. By reviving a century-old experimental paradigm with modern physics, engineering and immunologic tools, this work establishes a platform to dissect the mechanisms underlying airborne transmission of tuberculosis.