title: Changing pattern of clinical epidemiology on hepatitis C virus infection in southwest china.
abstract: BACKGROUND
  The changing pattern of hepatitis C virus (HCV) infection could have a significant impact on future medical prevention practices and therapies.
  
  
  OBJECTIVE
  The purpose of this study was to describe the changing pattern of HCV infection in southwest China using clinical epidemiology, and to assess the association between the genotypes distribution and certain potential risk factors.
  
  
  METHODS
  A retrospective analysis which included 1208 subjects with chronic HCV registered at the Southwest Hospital (Chongqing, Southwest China) was performed. The information was reviewed and the data collected from clinical records and short telephone interviews when necessary. 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 the patients' age, gender, risk exposure, and the initial risk exposure.
  
  
  RESULTS
  Among the 1 208 patients, the HCV subtype 1b was the most prevalent (32.9%), followed by subtype 3b (18.9%), 6a (18.0%), 3a (12.8%) and 2a (10.4%), while subtypes 1a and 6k accounted for cases of HCV infection in only 9 and 3 cases respectively. Individuals older than 40 years were mainly infected with subtypes 1b and 2a, whereas younger patients were predominantly infected with genotypes 3 and 6. Subtypes 1b and 2a were observed more frequently among 44.4% and 16.0% patients respectively, with a history of invasive operations. Subtypes 3b and 6a constituted the majority of HCV infections among intravenous drug users (IDUs) (28.7% and 34.9%, respectively). A significant difference (P < 0.001) was observed between the HCV genotype distributions, according to the potential route of infection.
  
  
  CONCLUSIONS
  In southwest China, the most common remaining subtype is the 1b genotype, but this has declined significantly among young patients. This is followed by subtype 3b and 6a which has increased significantly, especially among young patients. The distribution of such genotypes was also variable according to gender and age. The changing pattern of HCV infection was associated with changes in the modes of HCV acquisition, which raises an alarm signal concerning the major steps that need to be taken in order to reduce such infections in southwest China.
authors.affiliation: Institute of Infectious Diseases, Southwest Hospital, the Third Military Medical University, Chongqing, China.
authors.forename: Zehui
authors.initials: Z
authors.lastname: Yan
authors.forename: Ke
authors.initials: K
authors.lastname: Fan
authors.forename: Yuming
authors.initials: Y
authors.lastname: Wang
authors.forename: Yi
authors.initials: Y
authors.lastname: Fan
authors.forename: Zhaoxia
authors.initials: Z
authors.lastname: Tan
authors.forename: Guohong
authors.initials: G
authors.lastname: Deng