title: Multilevel and spatial analysis of syphilis in Shenzhen, China, to inform spatially targeted control measures.
abstract: OBJECTIVE
  The present study investigates the varied spatial distribution of syphilis cases in Shenzhen, China, and explores the individual-, neighbourhood- and district-level factors affecting the distribution.
  
  
  METHODS
  This study uses spatial analysis and multi-level generalised estimating equations to explore the spatial distribution of reported syphilis cases among individuals in Shenzhen, Guangdong Province, China. The spatial distribution of primary/secondary and latent cases was investigated using the Moran's I-statistic. Primary/secondary syphilis cases were compared with all syphilis cases using a three-level model with individual (n=6496), neighbourhood (n=55) and district (n=6) levels.
  
  
  RESULTS
  A total of 6496 syphilis cases were reported in 2009 with 35.8% primary and secondary syphilis cases. Both primary/secondary syphilis cases (Moran's I value=0.33, p<0.01) and latent syphilis cases (Moran's I value=0.19, p<0.01) showed significant spatial clustering at the neighbourhood level. Adjusting for the number of reporting hospitals, the best model found that the following characteristics were associated with primary/secondary syphilis infection: individuals who are younger in age (p=0.003), male (p<0.001), migrant labourers (p=0.047) and those who live in districts with a higher gross domestic product (p<0.001).
  
  
  CONCLUSIONS
  There is substantial clustering of primary and secondary syphilis cases at the neighbourhood level in Shenzhen, suggesting the need for greater STD health service provision in these clustered neighbourhoods. Spatially targeted syphilis control measures may be useful to optimise testing, treatment and partner services.
authors.affiliation: Shenzhen Center for Chronic Disease Control and Prevention, No.2021, Buxin Road, Luohu District, Shenzhen, Guangdong, China.
authors.forename: Xiaobing
authors.initials: X
authors.lastname: Wu
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Tucker
authors.forename: Fuchang
authors.initials: F
authors.lastname: Hong
authors.forename: Jane
authors.initials: J
authors.lastname: Messina
authors.forename: Lina
authors.initials: L
authors.lastname: Lan
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Hu
authors.forename: Tiejian
authors.initials: T
authors.lastname: Feng
authors.forename: Michael E
authors.initials: ME
authors.lastname: Emch
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Liu
authors.forename: Chunlai
authors.initials: C
authors.lastname: Zhang
authors.forename: Lizhang
authors.initials: L
authors.lastname: Wen
mesh_terms: D000328:Adult; D002681:China / Q000453:epidemiology; D016000:Cluster Analysis; D003140:Communicable Disease Control / Q000379:methods*; D005260:Female; D005843:Geography; D006801:Humans; D008297:Male; D008875:Middle Aged; D013587:Syphilis / Q000453:epidemiology* / Q000635:transmission