Spatial inequality, characteristics of internal migration, and pulmonary tuberculosis in China, 2011-2017: a spatial analysis

Abstract

Background: Human migration facilitate the spread of tuberculosis (TB). Migrants face an increased risk of TB infection. In this study, we aim to explore the spatial inequity of sputum smear-positive pulmonary TB (SS + PTB) in China; and the spatial heterogeneity between SS + PTB and internal migration.

Methods: Notified SS + PTB cases in 31 provinces in mainland China were obtained from the national web-based PTB surveillance system database. Internal migrant data were extracted from the report on China's migrant population development. Spatial autocorrelations were explored using the global Moran's statistic and local indicators of spatial association. The spatial variation in temporal trends was performed using Kulldorff's scan statistic. Fixed effect and spatial autoregressive models were used to explore the spatial inequity between SS + PTB and internal migration.

Results: A total of 2 380 233 SS + PTB cases were reported in China between 2011 and 2017, of which, 1 716 382 (72.11%) were male and 663 851 (27.89%) were female. Over 70% of internal migrants were from rural households and had lower income and less education. The spatial variation in temporal trend results showed that there was an 9.9% average annual decrease in the notification rate of SS + PTB from 2011 to 2017; and spatial clustering of SS + PTB cases was mainly located in western and southern China. The spatial autocorrelation results revealed spatial clustering of internal migration each year (2011-2017), and the clusters were stable within most provinces. Internal emigration, urban-to-rural migration and GDP per capita were significantly associated with SS + PTB, further, internal emigration could explain more variation in SS + PTB in the eastern region in mainland. However, internal immigration and rural-to-urban migration were not significantly associated with SS + PTB across China.

Conclusions: Our study found the spatial inequity between SS + PTB and internal migration. Internal emigration, urban-to-rural migration and GDP per capita were statistically associated with SS + PTB; the negative association was identified between internal emigration, urban-to-rural migration and SS + PTB. Further, we found those migrants with lower income and less education, and most of them were from rural households. These findings can help stakeholders to implement effective PTB control strategies for areas at high risk of PTB and those with high rates of internal migration.

Keywords: China; Internal migration; Pulmonary tuberculosis; Spatial analysis.

Fig. 1

Venn diagram of spatial–temporal statistics for SS + PTB in mainland China, 2011–2017. SS + PTB: Sputum smear-positive pulmonary tuberculosis

Fig. 2

The annual average notification rate of SS + PTB and the proportions of emigrants/immigrants at the province level in mainland China, 2011–2017. a Illustrates the notification rate of SS + PTB. b and c illustrate the proportions of emigrants and immigrants, respectively. TB tuberculosis; SS + PTB sputum smear-positive pulmonary TB

Fig. 3

The LISA cluster map of internal emigrants in China. a, b, c, d, e, f and g show the spatial clustering of emigrants in 2011–2017, respectively. LISA local indicator of spatial association

Fig. 4

The LISA cluster map of internal immigrants in China. a, b, c, d, e, f and g show the spatial clustering of immigrants in 2011–2017, respectively. LISA local indicator of spatial association

Fig. 5

The spatial variation in temporal trends of smear-positive PTB in China, 2011–2017. PTB pulmonary tuberculosis

Fig. 6

The internal migration flow of Beijing, Shanghai, Guangdong, Zhejiang, Fujian, Jiangsu, Jiangxi, and Guizhou provinces. a, b, c, d, e, and f present the immigrant flow of Beijing, Shanghai, Guangdong, Zhejiang, Fujian, and Jiangsu over 2011–2017, respectively. g and h present the emigrant flow of Jiangxi and Guizhou over 2011–2017, respectively. TB tuberculosis, SS + PTB sputum smear-positive pulmonary TB