title: Declining prevalence of HIV-infected individuals at risk of transmitting drug-resistant HIV in Denmark during 1997-2004.
abstract: BACKGROUND
  Transmission of drug-resistant HIV is a potential threat to the substantial clinical benefit of highly active antiretroviral therapy (HAART). To explore the background for the low rates of drug resistance transmission (2.5%) in our population, we estimated acquisition of HIV drug resistance and examined temporal trends in the prevalence of patients at risk of transmitting drug-resistant HIV.
  
  
  METHODS
  The study population included all 4,025 patients from The Danish HIV Cohort Study seen during the period 1995-2004. Virological failure to a given drug class was defined as a viral load (VL) > 1,000 copies/ml for 120 days while on a HAART regimen including that drug class. In addition, receiving nucleoside reverse transcriptase inhibitors (NRTIs) for 180 days before HAART counted as NRTI failure irrespective of VL. Having experienced failure was considered a proxy for harbouring drug-resistant virus in subsequent observation time. Patients with a current VL > 1,000 copies/ml were considered at risk of transmitting HIV.
  
  
  RESULTS
  We found a decrease from 1997 to 2004 in the prevalence of potential transmitters of drug-resistant HIV. The number of these patients with previous NRTI failure decreased from 429 (24% of all patients) in 1998 to 213 (8.0% of all patients) in 2004. Previous protease inhibitor (PI) failure peaked at 279 (14%) in 1999, declining to 142 (5.3%) in 2004. Previous NNRTI failure peaked at 121 patients (4.7%) in 2002, and occurred in 113 patients (4.2%) in 2004. Of all 686 potential transmitters in 2004, 31% had previously experienced NRTI failure, 21% PI failure, and 16% non-NRTI failure.
  
  
  CONCLUSIONS
  In the population of HIV-infected individuals in Denmark with complete follow-up, the number at risk of transmitting drug-resistant virus declined over time.
authors.affiliation: Odense University Hospital and University of Southern Denmark, Odense, Denmark. nicolai.lohse@ouh.fyns-amt.dk
authors.forename: Nicolai
authors.initials: N
authors.lastname: Lohse
authors.forename: Niels
authors.initials: N
authors.lastname: Obel
authors.forename: Gitte
authors.initials: G
authors.lastname: Kronborg
authors.forename: Louise Bruun
authors.initials: LB
authors.lastname: Jørgensen
authors.forename: Court
authors.initials: C
authors.lastname: Pedersen
authors.forename: Carsten Schade
authors.initials: CS
authors.lastname: Larsen
authors.forename: Birgit
authors.initials: B
authors.lastname: Kvinesdal
authors.forename: Henrik Toft
authors.initials: HT
authors.lastname: Sørensen
authors.forename: Jan
authors.initials: J
authors.lastname: Gerstoft
mesh_terms: D023241:Antiretroviral Therapy, Highly Active; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D004334:Drug Administration Schedule; D024921:Drug Resistance, Multiple, Viral; D005260:Female; D015658:HIV Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000635:transmission*; D017320:HIV Protease Inhibitors / Q000008:administration & dosage / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D015995:Prevalence; D018894:Reverse Transcriptase Inhibitors / Q000008:administration & dosage / Q000627:therapeutic use*; D017211:Treatment Failure; D019562:Viral Load
chemical_list: D017320:HIV Protease Inhibitors; D018894:Reverse Transcriptase Inhibitors