A 32-year-old woman with newly diagnosed sputum-positive pulmonary TB and a 28-year-old man with TB lymphadenitis (confirmed on lymph node biopsy) are both identified in a community survey in rural India. Which finding best discriminates the epidemiological significance of these two cases in terms of TB control priorities?

Question

Accepted Answer

D. The woman's sputum contains acid-fast bacilli; the man's lymph node does not shed bacilli into the environment. ## Epidemiological Significance: Shedding vs. Non-Shedding

**Key Point:** The critical discriminator for TB control priority is whether the case actively sheds infectious bacilli into the environment.

### Comparative Analysis

| Aspect | Sputum-Positive PTB | TB Lymphadenitis |
|--------|-------------------|------------------|
| **Bacillary shedding** | Yes (into respiratory secretions) | No (contained in lymph node) |
| **Infectiousness** | High (airborne transmission) | None (non-transmissible) |
| **Case priority** | **HIGH** (source case) | Low (dead-end host) |
| **Contact investigation** | **Mandatory** | Not indicated |
| **Isolation required** | Yes (respiratory) | No |

**High-Yield:** Sputum-positive PTB cases are the epidemiological drivers of TB transmission in communities. Each untreated sputum-positive case infects 10–15 contacts/year. TB lymphadenitis, despite being confirmed TB disease, contributes zero to community transmission [cite:Park 26e Ch 7; WHO TB Control Guidelines].

### Why This Matters for TB Control

1. **Case prioritization:** TB programs allocate resources to detect and treat sputum-positive cases first because they are the source of new infections.
2. **Contact tracing:** Only contacts of sputum-positive PTB patients are screened; contacts of EPTB patients are not.
3. **Surveillance classification:** In many TB registries, only PTB (especially sputum-positive) is counted toward TB incidence for epidemiological purposes.

**Clinical Pearl:** A sputum-positive PTB patient who remains untreated for 1 year will infect more people than 100 TB lymphadenitis cases combined. This is why case-finding strategies in TB programs focus on respiratory symptoms and sputum microscopy.

**Mnemonic:** **"Sputum = Spread; Lymph = Locked"** — PTB spreads; EPTB stays contained.

Answer

A. The woman has a higher risk of developing drug-resistant TB than the man

Answer

B. The woman has cavitary disease on chest X-ray; the man has non-cavitary lymph node involvement

Answer

C. The woman is more likely to have been infected through recent exposure; the man likely has remote infection

Explanation

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