title: The effect of churn on "community viral load" in a well-defined regional population.
abstract: BACKGROUND
  The concept of community viral load (CVL) was introduced to quantify the pool of transmissible HIV within a community and to monitor the potential impact of highly active antiretroviral therapy (HAART) on reducing new infections. The implications of churn (patient movement in/out of care in a community) on CVL have not been studied.
  
  
  METHODS
  The annual CVL was determined in the entire geographic HIV population receiving care in southern Alberta from 2001 to 2010; the CVL for specific subpopulations was analyzed for 2009. CVL was determined for patients under continuous care, newly diagnosed, new to the region, moved away, returned, and lost to follow-up (LTFU). Viral loads (VLs) <50 or <200 copies per milliliter were deemed undetectable and suppressed, respectively. The mean VL per patient and total VL were used to determine CVL.
  
  
  RESULTS
  From 2001 to 2010, the HAART uptake for all patients increased from 62% to 81%, undetectability from 32% to 66%, and suppression from 49% to 72%. The annual total CVL however did not vary significantly after 2003. Incidence rates for new locally diagnosed infections increased from 4.4 to 5.8/100,000 per year. In 2009, newly diagnosed HIV patients (6.6%) contributed 37.5% to the CVL, whereas patients transferring in/out of the region or lost to follow-up contributed 33% to the CVL. Patients in continuous care (79% of all patients) contributed 29.5% to the total CVL.
  
  
  CONCLUSIONS
  Increasing HAART coverage did not reduce the CVL or reduce new HIV diagnoses in our population. The effect of churn significantly limited CVL use as a measure for evaluating the impact of HAART in reducing HIV transmissions in our population.
authors.affiliation: *Southern Alberta Clinic, Calgary, Canada; and †Department of Medicine, University of Calgary, Calgary, Canada.
authors.forename: Hartmut B
authors.initials: HB
authors.lastname: Krentz
authors.forename: M John
authors.initials: MJ
authors.lastname: Gill
mesh_terms: D000293:Adolescent; D000328:Adult; D000416:Alberta / Q000453:epidemiology; D023241:Antiretroviral Therapy, Highly Active / Q000379:methods / Q000706:statistics & numerical data*; D004334:Drug Administration Schedule; D005260:Female; D015658:HIV Infections / Q000175:diagnosis / Q000188:drug therapy* / Q000635:transmission* / Q000821:virology; D015497:HIV-1 / Q000187:drug effects / Q000502:physiology*; D006291:Health Policy; D006801:Humans; D015994:Incidence; D008297:Male; D015995:Prevalence; D012367:RNA, Viral / Q000097:blood; D019562:Viral Load; D055815:Young Adult
chemical_list: D012367:RNA, Viral