Transmission of tuberculosis in rural Henan, China: a prospective population-based genomic spatial epidemiological study

The incidence of tuberculosis (TB) has declined more slowly in rural than urban areas in China, and data on the patterns of transmission and the high-risk populations in rural areas remains scarce. We conducted a population-based study of culture-positive pulmonary TB patients diagnosed in rural Linzhou City, Henan Province from July 2018 to February 2023. Genomic clusters were defined based on whole-genome sequencing and risk factors for clustering were identified by logistic regression. Transmission events were inferred with phybreak and transmission links were sought through epidemiological investigation of clustered patients. Logistic regression was used to explore the relationship between genomic differences of patient isolates and geographical distances of patient residences. Spatial hotspots were defined using kernel density estimation. Of 455 culture-positive patients, 430 were included in the final analysis. Overall, 192 (44.7%,192/430) patients were grouped into 49 clusters. Clusters containing ≥5 patients accounted for 18.4% (9/49) of the clusters and clustering was highest in student patients. No super-spreaders were detected. Confirmed epidemiologic links were identified for only 18.2% of clustered patients. The clustering risk decreased rapidly with increasing distances between patient residences, but 77.6% of clustered patient pairs lived ≥5.0 km apart. Both the Central Subdistrict and Rencun Township were identified as hotspots for TB transmission. Recent transmission appears to be an important driver of the TB burden in Linzhou. The formulation of effective strategies to reduce TB incidence in rural areas will require further studies to identify high-risk populations and venues where local inhabitants congregate and transmit the infection.