title: Analysis of the results of two nationwide surveys on Clonorchis sinensis infection in China.
abstract: OBJECTIVE
  To examine Clonorchis sinensis infection in China and evaluate the effectiveness of efforts to prevent and control it, two nationwide surveys were undertaken in 31 provinces, autonomous regions, and municipalities (PAMs) during 1988-92 (the 1990 survey) and during 2001-04 (the 2003 survey).
  
  
  METHODS
  During the period 2001-04, two sampling methods were applied. The first method repeated the stratified cluster random sampling used in the 1990 survey; the second method applied two-characteristic stratified cluster random sampling in 27 PAMs-the 2003 endemic area (EA) survey. The Kato-Katz thick smear method was used for the nationwide survey.
  
  
  RESULTS
  The infection rates of Clonorchis sinensis in the 1990 and 2003 surveys were 0.311% and 0.579%, respectively. The infection rate was 2.40% in the 2003 EA survey, and it was estimated that 12.49 million people in China were infected with Clonorchis sinensis.
  
  
  CONCLUSIONS
  The 2003 survey showed that the standardized infection rate of Clonorchis sinensis increased by 74.85% compared with the 1990 survey. The infection rate in males was higher than in females; the infection rate among people eating raw fish or eating out frequently was higher than among those who did not.
authors.affiliation: National Institute of Parasitic Disease, Chinese Center for Disease Control and Prevention, Shanghai 200025, China.
authors.forename: Ying Dan
authors.initials: YD
authors.lastname: Chen
authors.forename: Chang Hai
authors.initials: CH
authors.lastname: Zhou
authors.forename: Long Qi
authors.initials: LQ
authors.lastname: Xu
mesh_terms: D000818:Animals; D002681:China / Q000453:epidemiology; D003003:Clonorchiasis / Q000453:epidemiology* / Q000469:parasitology; D003004:Clonorchis sinensis / Q000302:isolation & purification*; D016000:Cluster Analysis; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male