title: Molecular characterization of HCV in a Swedish county over 8 years (2002-2009) reveals distinct transmission patterns.
abstract: BACKGROUND
  Hepatitis C virus (HCV) is a major public health concern and data on its molecular epidemiology in Sweden is scarce. We carried out an 8-year population-based study of newly diagnosed HCV cases in one of Sweden's centrally situated counties, Södermanland (D-county). The aim was to characterize the HCV strains circulating, analyze their genetic relatedness to detect networks, and in combination with demographic data learn more about transmission.
  
  
  METHODS
  Molecular analyses of serum samples from 91% (N=557) of all newly notified cases in D-county, 2002-2009, were performed. Phylogenetic analysis (NS5B gene, 300 bp) was linked to demographic data from the national surveillance database, SmiNet, to characterize D-county transmission clusters. The linear-by-linear association test (LBL) was used to analyze trends over time.
  
  
  RESULTS
  The most prevalent subtypes were 1a (38%) and 3a (34%). Subtype 1a was most prevalent among cases transmitted via sexual contact, via contaminated blood, or blood products, while subtype 3a was most prevalent among people who inject drugs (PWIDs). Phylogenetic analysis revealed that the subtype 3a sequences formed more and larger transmission clusters (50% of the sequences clustered), while the 1a sequences formed smaller clusters (19% of the sequences clustered), possibly suggesting different epidemics.
  
  
  CONCLUSIONS
  We found different transmission patterns in D-county which may, from a public health perspective, have implications for how to control virus infections by targeted interventions.
authors: Department of Microbiology, Public Health Agency of Sweden, Solna, Sweden; josefine.ederth@folkhalsomyndigheten.se.
authors: Josefine
authors: J
authors: Ederth
authors: Stockholm South General Hospital, Stockholm, Sweden.
authors: Camilla
authors: C
authors: Jern
authors: Department of Infectious Medicine, Institute of Biomedicine at Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors: Helené
authors: H
authors: Norder
authors: Department of Infectious Medicine, Institute of Biomedicine at Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors: Lars
authors: L
authors: Magnius
authors: Department of Microbiology, Public Health Agency of Sweden, Solna, Sweden.
authors: Erik
authors: E
authors: Alm
authors: Unilabs AB, Mälarsjukhuset Hospital, Eskilstuna, Sweden.
authors: Björg Kleverman
authors: BK
authors: Rognsvåg
authors: Department of Communicable Disease Control, Södermanland County, Sweden.
authors: Carl-Gustaf
authors: CG
authors: Sundin
authors: Department of Microbiology, Public Health Agency of Sweden, Solna, Sweden.
authors: Mia
authors: M
authors: Brytting
authors: Department of Microbiology Tumor and Cell Biology, Karolinska Institute, Stockholm, Sweden.|Nuffield Department Medicine, University of Oxford, Oxford, United Kingdom.
authors: Joakim
authors: J
authors: Esbjörnsson
authors: Department of Microbiology, Public Health Agency of Sweden, Solna, Sweden.
authors: Mattias
authors: M
authors: Mild
keywords: clusters; genotype; hepatitis C virus; networks; subtype; transmission