title: Changes in modes of hepatitis C infection acquisition and genotypes in southwest China.
abstract: BACKGROUND
  The shift in the distribution of HCV genotypes could have a significant impact on practical medical issues.
  
  
  OBJECTIVE
  To describe the recent distribution and evolution of HCV genotypes in southwest China.
  
  
  METHODS
  HCV genotypes were determined by nucleotide sequencing of the CE1 regions followed by phylogenic analysis with the published HCV genotype. HCV genotype distribution was analyzed according to patients' age, risk exposure, and the first time of risk exposure.
  
  
  RESULTS
  Among the 371 cases, subtypes 1a (0.8%), 1b (42.0%), 2a (9.7%), 3a (12.1%), 3b (21.0%), 4a (0.3%), and 6a (14.0%) were found. Genotypes 3 and 6 were significantly more frequent (85.4%) among IDUs than among other subjects (32.5%, P<0.001), they were also more frequent among subjects aged 40 years or under (63.6%) than older patients (21.6%, P<0.001), among patients infected after 1997 (54.4%) than those infected before 1997 (27.3%, P=0.001). Age 40 years or under (P<0.001) and infection via IDU (P<0.001) were independently associated with genotypes 3 and 6 in the multivariate stepwise logistic regression analysis. IDU was detected as a cause of infection in 27.8% of HCV cases; it was more frequent among younger patients (40.4%) than older ones (7.1%, P<0.001), among patients infected after 1997 (40.3%) than those infected before 1997 (16.2%, P<0.001).
  
  
  CONCLUSIONS
  In southwest China, the relative prevalence of genotypes 3 and 6 has increased significantly, and that of genotypes 1b and 2a has declined significantly among young patients. This shift in distribution was associated with changes in the modes of HCV acquisition.
authors.affiliation: Department of Infectious Diseases, Southwest Hospital, Third Military Medical University of Chinese People's Liberation Army, Chongqing 400038, China.
authors.forename: YouQian
authors.initials: Y
authors.lastname: Zhou
authors.forename: XiaoHong
authors.initials: X
authors.lastname: Wang
authors.forename: Qing
authors.initials: Q
authors.lastname: Mao
authors.forename: Yi
authors.initials: Y
authors.lastname: Fan
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhu
authors.forename: XuQing
authors.initials: X
authors.lastname: Zhang
authors.forename: Lin
authors.initials: L
authors.lastname: Lan
authors.forename: Li
authors.initials: L
authors.lastname: Jiang
authors.forename: WenTing
authors.initials: W
authors.lastname: Tan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001803:Blood Transfusion; D016009:Chi-Square Distribution; D002681:China / Q000453:epidemiology; D005260:Female; D005838:Genotype; D016174:Hepacivirus / Q000235:genetics*; D006526:Hepatitis C / Q000453:epidemiology / Q000635:transmission* / Q000821:virology; D006801:Humans; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D012367:RNA, Viral; D012044:Regression Analysis; D012307:Risk Factors; D015819:Substance Abuse, Intravenous
chemical_list: D012367:RNA, Viral