title: Emergence of Acquired HIV-1 Drug Resistance Almost Stopped in Switzerland: A 15-Year Prospective Cohort Analysis.
abstract: Drug resistance is a major barrier to successful antiretroviral treatment (ART). Therefore, it is important to monitor time trends at a population level.
  
  
  
  We included 11 084 ART-experienced patients from the Swiss HIV Cohort Study (SHCS) between 1999 and 2013. The SHCS is highly representative and includes 72% of patients receiving ART in Switzerland. Drug resistance was defined as the presence of ≥1 major mutation in a genotypic resistance test. To estimate the prevalence of drug resistance, data for patients with no resistance test was imputed based on the patient's risk of harboring drug-resistant viruses.
  
  
  
  The emergence of new drug resistance mutations declined dramatically from 401 to 23 patients between 1999 and 2013. The upper estimated prevalence limit of drug resistance among ART-experienced patients decreased from 57.0% in 1999 to 37.1% in 2013. The prevalence of 3-class resistance decreased from 9.0% to 4.4% and was always <0.4% for patients who initiated ART after 2006. Most patients actively participating in the SHCS in 2013 with drug-resistant viruses initiated ART before 1999 (59.8%). Nevertheless, in 2013, 94.5% of patients who initiated ART before 1999 had good remaining treatment options based on Stanford algorithm.
  
  
  
  Human immunodeficiency virus type 1 drug resistance among ART-experienced patients in Switzerland is a well-controlled relic from the era before combination ART. Emergence of drug resistance can be virtually stopped with new potent therapies and close monitoring.
authors.affiliation: Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich.|Institute of Medical Virology.
authors.forename: Alexandra U
authors.initials: AU
authors.lastname: Scherrer
authors.affiliation: Epidemiology, Biostatistics and Prevention Institute, University of Zurich.
authors.forename: Viktor
authors.initials: V
authors.lastname: von Wyl
authors.affiliation: Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich.|Institute of Medical Virology.
authors.forename: Wan-Lin
authors.initials: WL
authors.lastname: Yang
authors.affiliation: Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich.|Institute of Medical Virology.
authors.forename: Roger D
authors.initials: RD
authors.lastname: Kouyos
authors.affiliation: Institute of Medical Virology.
authors.forename: Jürg
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authors.lastname: Böni
authors.affiliation: Laboratory of Virology, Division of Infectious Diseases.
authors.forename: Sabine
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authors.lastname: Yerly
authors.affiliation: Department of Biomedicine, University of Basel.
authors.forename: Thomas
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authors.lastname: Klimkait
authors.affiliation: Division of Immunology and Allergy.
authors.forename: Vincent
authors.initials: V
authors.lastname: Aubert
authors.affiliation: Division of Infectious Diseases, University Hospital Lausanne.
authors.forename: Matthias
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authors.lastname: Cavassini
authors.affiliation: Division of Infectious Diseases and Hospital Epidemiology, University Hospital Basel.
authors.forename: Manuel
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authors.lastname: Battegay
authors.affiliation: Department of Infectious Diseases, Berne University Hospital and University of Berne.
authors.forename: Hansjakob
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authors.lastname: Furrer
authors.affiliation: HIV/AIDS Unit, Infectious Disease Service, Geneva University Hospital.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Calmy
authors.affiliation: Division of Infectious Diseases, Cantonal Hospital St Gallen.
authors.forename: Pietro
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authors.lastname: Vernazza
authors.affiliation: Division of Infectious Diseases, Regional Hospital Lugano, Switzerland.
authors.forename: Enos
authors.initials: E
authors.lastname: Bernasconi
authors.affiliation: Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich.|Institute of Medical Virology.
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authors.lastname: Schöni-Affolter
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authors.lastname: Trkola
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mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000494:pharmacology / Q000627:therapeutic use; D024882:Drug Resistance, Viral / Q000235:genetics*; D005260:Female; D015658:HIV Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000821:virology*; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011446:Prospective Studies; D013557:Switzerland / Q000453:epidemiology
chemical_list: D019380:Anti-HIV Agents
keywords: HIV-1 drug resistance; antiretroviral activity; emergence; prevalence; treatment-experienced patients