Combining environmental assessment and contact investigations to make tuberculosis screening decisions

SETTING: A combination of environmental measurement and mathematical modelling may provide a more quantitative method to inform the tuberculosis (TB) screening process in non-household settings following diagnosis of an infectious case. OBJECTIVE: To explore different methods for environmental assessment and mathematical modelling to predict TB transmission risk and devise a tool for public health practitioners for use in TB investigations. DESIGN: Parameters including air flow, carbon dioxide (CO₂) and airborne particles were measured over 3 working days in an office with a staff member with infectious TB. The Wells-Riley model was applied to predict transmission rates. RESULTS: The results suggested that poor ventilation and well-mixed air led to equal exposure of staff members to airborne TB bacilli. The model's prediction of attack rate (42%) supported the actual number of infections that occurred (50%). CONCLUSION: This study supports the use of environmental assessment and modelling as a tool for public health practitioners to determine the extent of TB exposure and to inform TB screening strategies. CO₂ and airborne particle profiles, both measured via a handheld device, provide the greatest practicality and amount of information that public health practitioners can use. Further studies will validate the level of screening required related to these measurements.