title: Estimates of HIV incidence among drug users in St. Petersburg, Russia: continued growth of a rapidly expanding epidemic.
abstract: BACKGROUND
  Russia has one of the world's fastest growing HIV epidemics and it has been largely concentrated among injection drug users (IDU). St Petersburg, Russia's second largest city, is one of the country's regions that has been most affected by the HIV epidemic. To monitor the current epidemic situation, we sought to estimate recent HIV incidence among IDU in St Petersburg.
  
  
  METHODS
  In a cross-sectional study of 691 IDU recruited during 2005-08, HIV incidence was estimated by two methods: a retrospective cohort analysis and BED capture enzyme immunoassay (EIA) results. Socio-demographic and behavioural correlates of incident infections and spatial patterns were examined.
  
  
  RESULTS
  In the retrospective cohort analysis, the incidence rate was estimated to be 14.1/100 person-years [95% confidence interval (CI) 10.7-17.6]. Using results of BED EIA and two correction formulas for known misclassification, incidence estimates were 23.9 (95% CI 17.8-30.1) and 25.5 (95% CI 18.9-32.0) per 100 person-years. Independent correlates of being recently infected included current unemployment (P = 0.004) and not having injected drugs in the past 30 days (P = 0.03). HIV incident cases were detected in all but one district in the city, with focal areas of transmission observed to be expanding.
  
  
  CONCLUSIONS
  High HIV incidence among IDU in St Petersburg attests to continued growth of the epidemic. The need for expansion of HIV prevention interventions targeted to vulnerable populations throughout the city is urgent. These results also suggest that the BED EIA may over-estimate incidence even after correction for low specificity.
authors.affiliation: Yale School of Public Health, Center for Interdisciplinary Research on AIDS, Yale University, New Haven, CT 06520, USA. linda.niccolai@yale.edu
authors.forename: Linda M
authors.initials: LM
authors.lastname: Niccolai
authors.forename: Sergei V
authors.initials: SV
authors.lastname: Verevochkin
authors.forename: Olga V
authors.initials: OV
authors.lastname: Toussova
authors.forename: Edward
authors.initials: E
authors.lastname: White
authors.forename: Russell
authors.initials: R
authors.lastname: Barbour
authors.forename: Andrei P
authors.initials: AP
authors.lastname: Kozlov
authors.forename: Robert
authors.initials: R
authors.lastname: Heimer
mesh_terms: D000293:Adolescent; D000328:Adult; D016739:Behavior, Addictive; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003710:Demography; D005260:Female; D006678:HIV; D015658:HIV Infections / Q000453:epidemiology*; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012426:Russia / Q000453:epidemiology; D012959:Socioeconomic Factors; D015819:Substance Abuse, Intravenous / Q000453:epidemiology*; D014505:Urban Population; D055815:Young Adult
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