Rural-to-urban migrant worker mobility shaped measles epidemics in China

Area of Science:

• Epidemiology
• Mathematical Modeling
• Public Health

Background:

• Measles outbreaks persist in China despite high routine childhood vaccination coverage.
• Rural-to-urban migrant workers are suspected contributors to measles transmission due to potentially lower vaccination rates in origin regions.

Purpose of the Study:

• To investigate the role of inter-Provincial-Level Administrative Division (PLAD) rural-to-urban migrant workers in measles epidemics in China (2005-2014).
• To identify epidemiological connections between origin and host PLADs facilitated by migrant mobility.
• To evaluate the impact of targeted vaccination strategies on measles control.

Main Methods:

• Developed a networked metapopulation Susceptible-Exposed-Infectious-Recovered (SEIR) model.
• Incorporated migrant worker mobility during Chinese New Year (CNY) and year-round traveler mobility.
• Simulated measles transmission dynamics within migrant subpopulations and performed counterfactual analyses.

Main Results:

• Migrant workers from Hebei and Shandong were key contributors to measles outbreaks in Beijing and Tianjin.
• Migrant workers from Anhui and Sichuan contributed to outbreaks across multiple southern PLADs.
• Measles epidemics were sustained by under-vaccinated migrant inflows during CNY; returning migrants facilitated synchronized epidemics in origin PLADs.

Conclusions:

• Rural-to-urban migrant workers play a critical role in sustaining and spreading measles epidemics in China.
• Targeted vaccination strategies, particularly for migrant populations, are essential for effective measles control.
• Understanding migration dynamics is crucial for designing public health interventions in regions with similar mobility patterns.