Spread of Mycobacterium Tuberculosis Lineage 4 in Sichuan-chongqing Region of China Influenced by Maritime Silk Road and “huguang Filling Sichuan” 

Abstract BackgroundThe spread of Mycobacterium tuberculosis complex (MTBC) was closely influenced by human migration. Lineage 4, a lineage of MTBC mainly being epidemic in Europe and America, was not the major one in China. Its proportion in Sichuan-Chongqing region, however, was significantly higher than that at the national level. Previous study by the most recent common ancestor calculation based on Bayes model suggested that lineage 4 epidemic in South China today probably entered China around the 13th century, and the most important human migration events associating with this region during and after this period of time included Maritime Silk Road and “Huguang filling Sichuan”. The purpose of this study was to explore whether the high proportion of lineage 4 in Sichuan-Chongqing region was impacted by these two events. MethodsThe genotyping data of 17,269 MTBC isolates, the proportion of targeted surname populations related to “Huguang filling Sichuan”, and the information of main ports’ location around Maritime Silk Road were collected. Interpolation analysis was used to estimate the geographical distribution of lineage 4 and its three sub-lineages (L4.2, L4.4, L4,5), as well as the targeted surname populations. And the correlation between the geographical distribution in the main ports on Maritime Silk Road and the regions with the proportion of L4.2 and L4.4 was analyzed.ResultsInterpolation and correlation analysis showed that lineage 4’s distribution in China could be mapped to the regions affected by “Huguang filling Sichuan”, while L4.2 and L4.4’s distributing in Asia, Europe, and Africa could be those by Maritime Silk Road, ConclusionsMaritime Silk Road and “Huguang Filling Sichuan” potentially posed an essential combined influence on the greater occurring of lineage 4 in Sichuan-Chongqing region. This study may contribute to the tracing and epidemiological investigation of tuberculosis and other world-wide infectious diseases.