A 32-year-old male construction worker from rural Maharashtra presents with a 3-week history of productive cough with blood-tinged sputum, low-grade fever in the evenings, and night sweats drenching his clothes. He lives in a crowded 1-room tenement with 6 family members. His 8-year-old daughter was treated for tuberculosis 6 months ago. On examination, he is cachectic with crackles in the right upper lobe. Sputum smear microscopy shows acid-fast bacilli (2+ on Ziehl-Neelsen staining). What is the epidemiological classification of this case in the context of TB control programs?

Explanation

## Case Classification in TB Epidemiology **Key Point:** A patient with no prior history of TB treatment who presents with bacteriologically confirmed pulmonary TB (sputum smear positive) is classified as a **new case** according to WHO and NTEP (National TB Elimination Program) definitions. ### Definitions of TB Cases | Classification | Definition | Sputum Status | |---|---|---| | **New case** | No prior TB treatment or <1 month of prior treatment | Can be smear +ve or −ve | | **Relapse** | Completed treatment, bacteriologically cured, now smear +ve again | Smear positive | | **Treatment failure** | Remains smear +ve after 5 months of standard therapy | Smear positive | | **Chronic case** | Smear +ve after treatment failure category management | Smear positive | | **Previously treated (not relapse)** | Interrupted treatment, lost to follow-up, or other prior TB | Variable | **Clinical Pearl:** The presence of a previously treated contact (his daughter) increases the likelihood of recent transmission and supports the diagnosis of active TB in this patient, but does not change his classification as a new case since he has no personal history of TB treatment. **High-Yield:** In India's NTEP framework, new cases are further sub-classified by site (pulmonary vs. extrapulmonary) and bacteriological status (smear +ve, smear −ve culture +ve, or clinically diagnosed). This patient is a **new pulmonary TB, smear-positive case** — the highest priority for treatment and contact tracing. ### Why This Classification Matters 1. **Treatment regimen:** New cases receive standard 6-month therapy (2HRZE/4HR) 2. **Epidemiological significance:** Smear-positive cases are the most infectious and drive TB transmission 3. **Contact tracing:** Mandatory investigation of household contacts (his 6 family members and daughter) 4. **Cure definition:** Completion of treatment with bacteriological conversion **Mnemonic:** **NEW = No prior treatment Exposure With active disease**