BACKGROUND:
Tuberculosis (TB) remains a major infectious disease globally 1. In Chile, TB incidence has increased in recent years, representing a setback in disease control 2. Passive case-finding strategies have been identified as a key challenge 3; however, no standardized methodological framework exists to guide territorial prioritization. This study aimed to conduct a national estimation of pulmonary TB risk at small geographic scales between 2016 and 2024, providing critical evidence to support targeted case-finding strategies.

METHODS:
We conducted an ecological study, geocoding cases using a cascade strategy and aggregating them by census district. Spatial autocorrelation was assessed using Moran’s I, and small-area risk was estimated using hierarchical Bayesian Poisson spatial models implemented with INLA in R 4. Sociodemographic covariates were obtained from the most recent national census data (2024).

RESULTS:
We analyzed 2,762 census districts, and 80.5% (n=17.095) of cases were successfully geocoded; among these, 34.7% were women and 65.3% men, with a mean age of 46.3 years. Significant spatial autocorrelation was observed (Moran’s I=0.53; p<0.001). Overcrowding showed the strongest association with TB risk (RR per +1%=1.117). Indigenous population proportion was inversely associated (RR=0.972), while population aged ≥60 years showed a small but consistent effect (RR=1.009). No independent effect of immigrant population proportion was observed.

CONCLUSIONS:
Spatial analysis revealed strong clustering of pulmonary TB in Chile. Overcrowding was the most robust determinant of increased TB risk, while age structure contributed a smaller but consistent effect. These findings highlight the importance of incorporating housing conditions and demographic structure into territorial prioritization strategies. Small-area risk estimates provide actionable evidence to guide community-based active case finding and improve the efficiency of TB control interventions at the national level.