What is the difference between open and closed TB?

• A. Closed: TB in Lymph, Not Contagious
• B. Closed: TB Lesion in Lungs, Sputum Positive
• C. Open: TB Lesion in Lungs, Coughing Sputum with TB Bacteria
• D. Open: TB in Lymph, Not Contagious

Answer: (C)

Open tuberculosis refers to active pulmonary disease where the bacteria are present in the sputum and can be coughed up and spread to others. This contagious stage arises when there is an infectious load in the airways, often with a lung lesion that releases Mycobacterium tuberculosis in the sputum. That’s why the description of a lung lesion with coughing sputum containing TB bacteria best captures what makes TB contagious.

In contrast, closed TB is non-contagious because the bacteria are not being shed in the sputum; this can correspond to latent infection or to extrapulmonary forms where the lungs aren’t releasing bacilli into the airway. The other options describe scenarios that don’t align with contagious pulmonary TB.