Epidemiological characteristics of tuberculosis among migrant populations and key predictors of migratory cases in Zhejiang Province.

OBJECTIVES

Population mobility poses challenges to tuberculosis (TB) control. As a major destination for internal migrants in China, Zhejiang Province bears a substantial burden of migrant TB cases. This study aimed to characterize TB epidemiology in Zhejiang Province and identify key predictors of migratory TB cases.

METHODS

TB surveillance data from the Tuberculosis Information Management System (TBIMS) of Zhejiang Province for 2005-2023 were analyzed using joinpoint regression, age-period-cohort modeling, and spatial analyses to characterize temporal, demographic, and spatial patterns and compare migrant and local TB cases. Boosted regression tree (BRT) modeling was used in a case-case design to identify individual- and municipal-level predictors of migratory status among TB cases and quantify their relative contributions.

RESULTS

The average annual TB incidence was 61.35 per 100,000 population, and migrant TB cases accounted for 34.48% of all reported cases. TB incidence increased during 2005-2007 with an annual percent change (APC) of 2.76%, and subsequently declined during 2007-2023 (APC = -4.12%). The proportion of migrant TB cases increased through 2019 (APC = 5.83%) and then declined sharply during 2019-2023 (APC = -17.62%). Age-period-cohort analysis revealed a bimodal age effect, with peaks at 15-19 and 75-79 years, while cohort effects were elevated among cohorts born from the late 1940s through the 1970s and subsequently declined. Spatial autocorrelation in TB incidence increased from 2010 onward, while local and migrant TB case proportions clustered mainly in Quzhou and Lishui and in Ningbo and Jiaxing, respectively. Gross regional product (GRP) per capita was the leading predictor of migratory TB cases (57.5%), followed by the immigration index (9.0%), city type (6.8%), and tertiary industry proportion of GRP (5.9%), with marked variation in relative contributions across origin regions.

CONCLUSIONS

TB incidence declined overall in Zhejiang Province, but migrant TB cases remained epidemiologically important and showed distinct demographic and spatial patterns. GRP per capita was the leading predictor, with additional contributions from population mobility indicators and marked variation across origin regions. These findings support coordinated cross-regional surveillance, continuity of TB care, and strategies adapted to local population structures and mobility patterns.