title: Geospatial characteristics of measles transmission in China during 2005-2014.
abstract: Measles is a highly contagious and severe disease. Despite mass vaccination, it remains a leading cause of death in children in developing regions, killing 114,900 globally in 2014. In 2006, China committed to eliminating measles by 2012; to this end, the country enhanced its mandatory vaccination programs and achieved vaccination rates reported above 95% by 2008. However, in spite of these efforts, during the last 3 years (2013-2015) China documented 27,695, 52,656, and 42,874 confirmed measles cases. How measles manages to spread in China-the world's largest population-in the mass vaccination era remains poorly understood. To address this conundrum and provide insights for future public health efforts, we analyze the geospatial pattern of measles transmission across China during 2005-2014. We map measles incidence and incidence rates for each of the 344 cities in mainland China, identify the key socioeconomic and demographic features associated with high disease burden, and identify transmission clusters based on the synchrony of outbreak cycles. Using hierarchical cluster analysis, we identify 21 epidemic clusters, of which 12 were cross-regional. The cross-regional clusters included more underdeveloped cities with large numbers of emigrants than would be expected by chance (p = 0.011; bootstrap sampling), indicating that cities in these clusters were likely linked by internal worker migration in response to uneven economic development. In contrast, cities in regional clusters were more likely to have high rates of minorities and high natural growth rates than would be expected by chance (p = 0.074; bootstrap sampling). Our findings suggest that multiple highly connected foci of measles transmission coexist in China and that migrant workers likely facilitate the transmission of measles across regions. This complex connection renders eradication of measles challenging in China despite its high overall vaccination coverage. Future immunization programs should therefore target these transmission foci simultaneously.
authors.affiliation: Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York, United States.
authors.forename: Wan
authors.identifier: 0000-0002-7555-9728
authors.initials: W
authors.lastname: Yang
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, P.R. China.
authors.forename: Liang
authors.initials: L
authors.lastname: Wen
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, P.R. China.
authors.forename: Shen-Long
authors.initials: SL
authors.lastname: Li
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, P.R. China.
authors.forename: Kai
authors.initials: K
authors.lastname: Chen
authors.affiliation: Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, P.R. China.
authors.forename: Wen-Yi
authors.initials: WY
authors.lastname: Zhang
authors.affiliation: Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York, United States.
authors.forename: Jeffrey
authors.identifier: 0000-0002-7216-7809
authors.initials: J
authors.lastname: Shaman
mesh_terms: D002681:China / Q000453:epidemiology; D016000:Cluster Analysis; D004196:Disease Outbreaks; D006801:Humans; D015994:Incidence; D008457:Measles / Q000453:epidemiology / Q000635:transmission*; D011159:Population Surveillance; D012923:Social Class