Exposure to TB Bacilli

Patients suffering from microbiologically confirmed pulmonary TB (PTB) constitutes the most important source of infection.

• The infection occurs most commonly through droplet nuclei generated by coughing, sneezing etc., inhaled via the respiratory route.
• M. tuberculosis spreads from the respiratory tract in small respiratory droplets or within dust particles that can travel long distances in the air.

Figure: How Exposure to TB Bacilli Happens

The chances of getting exposed and infected depend on the: 

• Duration of exposure to an active TB patient
• Frequency of exposure
• Bacterial load of the TB patient
• Virulence of TB bacilli
• Immune status of the exposed individual
• Other factors (air circulation, overcrowding, temperature and humidity etc.)

Resources

• Robbin's Basic Pathology, 10th Edition, 2018.
• Training Module (1-4) for Program Managers and Medical Officer, NTEP, MoHFW, 2020.

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