Internal migrants as drivers of long-distance cross-regional transmission of tuberculosis in China

Objectives Internal migrants in China frequently travel between their hometowns and the cities where they work, creating ample opportunities for cross-regional transmission of tuberculosis (TB). The aim of this study was to explore the role of internal migrants in transmitting TB across different regions and the contribution of cross-region transmission to China's TB burden. Methods The study included a total of 8664 patients with TB and their Mycobacterium tuberculosis isolates, collected from two large cities and three rural regions. Genomic clusters were defined as having a genomic distance of ≤12-single nucleotide polymorphisms. Cross-regional clusters were defined as clusters containing patients from at least two regions, indicative of cross-regional transmission. Results A total of 2403 clustered cases (27.7%) were grouped into 845 clusters, of which 142 (16.8%) were cross-regional. An increased risk for cross-regional transmission was found for internal migrants (adjusted OR (aOR), 1.45; 95% CI, 1.13-1.87), individuals aged Discussion The mobility of the internal migrant population appears to be responsible for most cross-regional transmission of TB in China. The magnitude and dynamics of cross-regional transmission should be addressed in future strategies to reduce the incidence of TB in China.