Annual New Case Detection Rate (ANCDR) per 100,000 population remains a critical indicator for monitoring progress under India’s National Leprosy Eradication Programme (NLEP). While Tamil Nadu as a state has maintained relatively low ANCDR, Chennai district, a metropolitan and purely urban setting, presents unique challenges due to large-scale migrant settlements, high mobility, and floating population. Notably, child ANCDR in the district has been consistently higher compared to the state average, suggesting active transmission. This study describes the epidemiological profile and spatial distribution of new leprosy cases across the 15 administrative zones of Chennai during 2021–2025, with reference to time, place, and person distribution.
Methods : Secondary data were extracted from official programme registers for the fiscal years 2021–2025. Variables included age, gender, type of leprosy, presence of deformity, and mode of case detection. Population denominators were derived from 2011 Census projections, disaggregated by age and gender. ANCDR was calculated annually and stratified by zone, age group, gender, and type of leprosy. Special attention was given to industrial and border zones to understand spatial clustering.
RESULTS: A total of 515 new leprosy cases were reported during the five-year period. The overall ANCDR ranged from 1.0 per 100,000 in 2020–21 to 1.3 in 2024–25, with a transient peak above 2.0 during 2022–23. Spatial analysis showed six zones reporting ANCDR >2.0, three of which were industrial hubs and three located at district borders (range: 2.0–4.9). Child ANCDR was notably high, ranging from 3.5 to 11.5, especially in industrial, their adjoining residential zone and border zones. Multibacillary (MB) cases constituted more than 50% of all detections, with MB ANCDR remaining stable across zones (approximately 1.2). Paucibacillary (PB) cases were more common in the <15-year age group (1.5 per 100,000). No cases were reported among listed household or neighborhood contacts despite systematic screening.
CONCLUSION: Surveillance in Chennai shows static overall ANCDR but persistent hotspots in industrial and border zones with elevated child ANCDR, indicating ongoing transmission likely linked to migrants. Stable MB rates and absence of contact cases suggest transmission beyond households. Conventional case-finding may miss such foci, underscoring the need for innovative surveillance strategies targeting migrant populations to sustain elimination goals.