Municipality-level spatial clustering and socio-environmental determinants of tuberculosis in Nepal, 2019–2024

Abstract

Tuberculosis (TB) remains a major public health challenge in Nepal, marked by substantial geographic heterogeneity. Despite ongoing control efforts, spatial clustering patterns and socio-environmental determinants at the municipal level are not well understood. This study assessed spatial clustering of TB notification rates and their association with sociodemographic, housing, and environmental factors across all 753 municipalities of Nepal. Data of notified TB cases were extracted from National Tuberculosis Control Centre from FY 2019/20 to FY 2023/24. Spatial autocorrelation analyses were conducted using annual TB notification rates, while spatial regression models were based on five-year averaged data. Spatial autocorrelation and clustering were examined using Global Moran’s I, Getis-Ord Gi*, and Local Indicators of Spatial Association (LISA). Associations between TB notification rates and socio-demographic, housing, and environmental factors were evaluated using Ordinary Least Squares, Spatial Lag, and Spatial Error Models. A total of 172,155 TB cases were reported over the five-year period (FY 2019/20-2023/24), with national notification rates increasing from 92 to 139 per 100,000 population. Significant and persistent positive spatial autocorrelation was observed annually (Moran’s I: 0.42-0.53; p < 0.001). High-High clusters were consistently concentrated in the densely populated Terai municipalities of Madhesh and Lumbini Provinces, whereas Low-Low clusters dominated the remote mountain regions of Karnali and Sudurpashchim. The Spatial Error Model (SEM) provided the best fit (Pseudo-R² = 0.62), revealing that population density (β=0.005, p<0.001), liquefied petroleum gas use (β=60.85, p<0.001), and nighttime land surface temperature (β=1.69, p<0.05) were significantly associated with higher TB notification rates. Traditional housing materials (mud walls: β=-38.40, p<0.001) and cow dung fuel use (β=-48.43, p<0.05) showed negative associations, this may reflect diagnostic access barriers rather than lower disease incidence. Tuberculosis in Nepal demonstrates significant and persistent spatial clustering at the local municipal level, driven by population density, housing, energy access, and climatic conditions. These results emphasize the need for geographically targeted, municipality-focused interventions to advance Nepal’s progress toward the End TB Strategy and Sustainable Development Goal 3.3 Not applicable.