The reasoning: epidemiology
| Feature | Detail |
|---|---|
| Agent | M. leprae (and M. lepromatosis); obligate intracellular; prefers cooler body parts (skin, peripheral nerves, nasal mucosa); generation time ≈ 12–14 days; not culturable in vitro (mouse footpad, armadillo) |
| Reservoir | Untreated MB patients (nasal discharge); armadillos in the Americas |
| Transmission | Mainly droplets from the upper respiratory tract with prolonged close contact; skin contact less important |
| Incubation | Long: 2–5 years on average (PB), longer for MB (up to 20 years) |
| Host factors | Most people are naturally resistant; genetic susceptibility; household contacts of MB patients have the highest risk |
| Burden | India reports > 50% of the world's new cases; national prevalence < 1/10,000 since December 2005, but some districts remain above it |