title: Systematic review and meta-analysis of hepatitis C virus infection and HIV viral load: new insights into epidemiologic synergy.
abstract: Hepatitis C virus (HCV) and HIV infection frequently co-occur due to shared transmission routes. Co-infection is associated with higher HCV viral load (VL), but less is known about the effect of HCV infection on HIV VL and risk of onward transmission.
  
  
  
  We undertook a systematic review comparing 1) HIV VL among ART-naïve, HCV co-infected individuals versus HIV mono-infected individuals and 2) HIV VL among treated versus untreated HCV co-infected individuals. We performed a random-effects meta-analysis and quantified heterogeneity using the I(2) statistic. We followed Cochrane Collaboration guidelines in conducting our review and PRISMA guidelines in reporting results.
  
  
  
  We screened 3925 articles and identified 17 relevant publications. A meta-analysis found no evidence of increased HIV VL associated with HCV co-infection or between HIV VL and HCV treatment with pegylated interferon-alpha-2a/b and ribavirin.
  
  
  
  This finding is in contrast to the substantial increases in HIV VL observed with several other systemic infections. It presents opportunities to elucidate the biological pathways that underpin epidemiological synergy in HIV co-infections and may enable prediction of which co-infections are most important to epidemic control.
authors.affiliation: London School of Economics, University of London, London, UK.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Petersdorf
authors.affiliation: Division of Infectious Diseases, University of Washington, Seattle, WA, USA; jross3@uw.edu.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Ross
authors.affiliation: MRC Tropical Epidemiology Group, Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, University of London, London, UK.
authors.forename: Helen A
authors.initials: HA
authors.lastname: Weiss
authors.affiliation: Division of Infectious Diseases, University of Washington, Seattle, WA, USA.|Department of Epidemiology, University of Washington, Seattle, WA, USA.|Department of Global Health, University of Washington, Seattle, WA, USA.
authors.forename: Ruanne V
authors.initials: RV
authors.lastname: Barnabas
authors.affiliation: Division of Infectious Diseases, University of Washington, Seattle, WA, USA.|Department of Epidemiology, University of Washington, Seattle, WA, USA.|Department of Global Health, University of Washington, Seattle, WA, USA.
authors.forename: Judith N
authors.initials: JN
authors.lastname: Wasserheit
mesh_terms: D000998:Antiviral Agents / Q000627:therapeutic use; D060085:Coinfection / Q000188:drug therapy; D015658:HIV Infections / Q000150:complications / Q000188:drug therapy / Q000453:epidemiology / Q000821:virology*; D016174:Hepacivirus; D006526:Hepatitis C / Q000150:complications / Q000453:epidemiology / Q000821:virology*; D006801:Humans; D019562:Viral Load
chemical_list: D000998:Antiviral Agents
keywords: HCV; HIV; co-infection; hepatitis C virus; systematic review; viral load