Mapping the distribution of tuberculosis cases identified through routine program and community based active screening in Central Ethiopia

Abstract

Background Smear positive TB cases greatly contribute to community level transmission of the disease. Locating hotspots would make it easier to prioritize and target control interventions. This study is aimed at assessing the spatial distribution of smear positive index TB cases and their secondary cases and the predictors of clustering of smear positive TB cases. Methods The study was conducted in Silti Zone of Central Ethiopia from 2020–2022. Data of smear positive index TB cases were collected from the unit TB registers of healthcare facilities. Contacts of all index TB cases were screened in the community and tested to identify secondary TB cases. We performed spatial analysis including Moran’s I statistic, Getis-Ord Gi* statistic and geographically weighted regression (GWR) to assess the global distribution, local clustering and the predictors of clustering of smear positive TB cases respectively. Additionally, we used inverse distance weighting (IDW) interpolation to predict the distribution of smear postive TB cases and develop a continuous raster map for places with no data. Results Spatial autocorrelation results showed that the distribution of the smear positive TB cases showed signficant clustering (Moran’s I = 0.70029; p-value < 0.000). The Getis-Ord Gi* output indicated the presence of statistically significant hotspots as well as cold spots in the study area. Statistically significant hotspots were found in 11 Kebeles of Silti, Dalocha and Misrak Silti districts. Signficant coldspots were also found in five kebeles of the Silti and Misrak districts. GWR analysis revealed that no education, primary education, family size and thatched roof houses were significant predictors of the spatial clustering of the smear positive TB cases. We also found that majority of the secondary TB cases were found in the hotspot areas identified through the spatial analysis. Conclusion Our study showed that the distribution of smear positive TB cases in the study area was heterogenous and both statistically significant hotspots and coldspots were identified. Location based targeted interventions could improve TB control performances including reduction in the transmission of TB. Educational status, family size and housing type were some of the factors with significant influence on the spatial distribution of smear positive TB in the study area. Distribution of the secondary TB cases found through household contacts screening coincided with the identified hotspots indicating higher transmission of the disease in these places.