From the Guidelines
Tuberculosis thrives in poorly ventilated, crowded indoor environments, which significantly increases the risk of airborne transmission of Mycobacterium tuberculosis. When an infected person coughs, sneezes, or speaks, they release tiny droplets containing the bacteria into the air. In crowded spaces, people are in close proximity to potentially infected individuals, increasing exposure risk. Poor ventilation means these contaminated droplets remain suspended in the air longer and recirculate rather than being filtered out or replaced with fresh air. The risk of tuberculosis transmission depends on the concentration of the tubercle bacilli in the air, the airflow, the duration of the contact, and the susceptibility of the contact to infection 1.
Key factors that enhance the likelihood of transmission include exposure in relatively small, enclosed spaces, inadequate local or general ventilation, and recirculation of air containing infectious droplet nuclei 1. Characteristics of the TB patient that enhance transmission include disease in the lungs, airways, or larynx, presence of cough or other forceful expiratory measures, and presence of acid-fast bacilli (AFB) in the sputum 1.
To minimize the risk of transmission, it is essential to implement environmental controls, such as controlling the source of infection using local exhaust ventilation and diluting and removing contaminated air using general ventilation 1. Additionally, secondary environmental controls, including controlling the airflow to prevent contamination of air in areas adjacent to the source and cleaning the air using HEPA filtration and/or UVGI, can be effective 1.
In real-life clinical practice, prioritizing ventilation and minimizing crowding in indoor environments is crucial to reduce the risk of tuberculosis transmission. This can be achieved by ensuring adequate ventilation, using HEPA filters, and implementing UVGI in high-risk areas, such as healthcare facilities, shelters, and correctional facilities 1. By taking these measures, we can significantly reduce the risk of tuberculosis transmission and improve outcomes for individuals at risk.
From the Research
Relationship between Tuberculosis Prevalence and Poorly Ventilated, Crowded Indoor Environments
- Tuberculosis (TB) transmission is facilitated in overcrowded, poorly ventilated congregate settings, such as hospitals, clinics, prisons, jails, and refugee camps 2.
- The risk of TB transmission is increased in environments with poor ventilation, as seen in prisons where cells are densely populated and poorly ventilated 3.
- Factors that contribute to the risk of TB in an institution include the entrance-point prevalence of infection, the potential for reactivation, and the role of transmission within the institution, as well as the potential for detection, prevention, and treatment of disease 4.
- Poorly ventilated environments increase the risk of TB transmission, as airborne droplet nuclei can be more easily transmitted in these settings 5.
Impact of Ventilation on Tuberculosis Transmission
- Improving ventilation to World Health Organization (WHO) standards can decrease TB transmission by 38.2%, while optimizing cross-ventilation can reduce transmission by 64.4% 3.
- Natural ventilation is the main means of air disinfection and has the advantage of wide availability, low cost, and high efficacy under optimal conditions 2.
- Mechanical ventilation, if properly installed and maintained, can provide adequate air disinfection, but it is expensive to install, maintain, and operate 2.
Control Strategies for Tuberculosis in Crowded Environments
- Control strategies for hospitals, nursing homes, prisons, and chronic care facilities include entrance-point skin testing, contact testing, periodic retesting, supervised preventive therapy, effective treatment of disease, and the selective application of ultraviolet air disinfection for certain high-risk areas 4.
- In inner-city shelters and jails, control strategies shift to disease detection, isolation, effective long-term treatment, reduced crowding, ultraviolet air disinfection, and periodic testing and treatment of staff 4.