title: Correlates of injecting in an HIV incidence hotspot among substance users in Tijuana, Mexico.
abstract: BACKGROUND
  Substance use and HIV are growing problems in the Mexico-U.S. border city of Tijuana, a sex tourism destination situated on a northbound drug trafficking route. In a previous longitudinal study of injection drug users (IDUs), we found that >90% of incident HIV cases occurred within an 'HIV incidence hotspot,' consisting of 2.5-blocks. This study examines behavioral, social, and environmental correlates associated with injecting in this HIV hotspot.
  
  
  METHODS
  From 4/06 to 6/07, IDUs aged ≥18 years were recruited using respondent-driven sampling. Participants underwent antibody testing for HIV and syphilis and interviewer-administered surveys eliciting information on demographics, drug use, sexual behaviors, and socio-environmental influences. Participants were defined as injecting in the hotspot if they most frequently injected within a 3 standard deviational ellipse of the cohort's incident HIV cases. Logistic regression was used to identify individual and structural factors associated with the HIV 'hotspot'.
  
  
  RESULTS
  Of 1031 IDUs, the median age was 36 years; 85% were male; HIV prevalence was 4%. As bivariate analysis indicated different correlates for males and females, models were stratified by sex. Factors independently associated with injecting in the HIV hotspot for male IDUs included homelessness (AOR 1.72; 95%CI 1.14-2.6), greater intra-urban mobility (AOR 3.26; 95%CI 1.67-6.38), deportation (AOR 1.58; 95%CI 1.18-2.12), active syphilis (AOR 3.03; 95%CI 1.63-5.62), needle sharing (AOR 0.57; 95%CI 0.42-0.78), various police interactions, perceived HIV infection risk (AOR 1.52; 95%CI 1.13-2.03), and health insurance status (AOR 0.53; 95%CI 0.33-0.87). For female IDUs, significant factors included sex work (AOR 8.2; 95%CI 2.2-30.59), lifetime syphilis exposure (AOR 2.73; 95%CI 1.08-6.93), injecting inside (AOR 5.26; 95%CI 1.54-17.92), arrests for sterile syringe possession (AOR 4.87; 95%I 1.56-15.15), prior HIV testing (AOR 2.45; 95%CI 1.04-5.81), and health insurance status (AOR 0.12; 95%CI 0.03-0.59).
  
  
  CONCLUSIONS
  While drug and sex risks were common among IDUs overall, policing practices, STIs, mobility, and lack of healthcare access were correlated with injecting in this HIV transmission hotspot. Although participants in the hotspot were more aware of HIV risks and less likely to report needle sharing, interventions addressing STIs and structural vulnerabilities may be needed to effectively address HIV risk.
authors.affiliation: Division of Global Public Health, Department of Medicine, University of California, San Diego, 9500 Gilman Drive, MC 0507, La Jolla, CA 92093-0507, USA; Graduate School of Public Health, San Diego State University, Hardy Tower 119, 5500 Campanile Drive, San Diego, CA 92182-4162, USA.
authors.forename: Nana
authors.initials: N
authors.lastname: Kori
authors.affiliation: Division of Global Public Health, Department of Medicine, University of California, San Diego, 9500 Gilman Drive, MC 0507, La Jolla, CA 92093-0507, USA.
authors.forename: Alexis M
authors.initials: AM
authors.lastname: Roth
authors.affiliation: Pro-COMUSIDA, Niños héroes 697, Oficina 1 y 6, Zona Norte, Tijuana 22000, Baja California, Mexico.
authors.forename: Remedios
authors.initials: R
authors.lastname: Lozada
authors.affiliation: Division of Global Public Health, Department of Medicine, University of California, San Diego, 9500 Gilman Drive, MC 0507, La Jolla, CA 92093-0507, USA.
authors.forename: Alicia
authors.initials: A
authors.lastname: Vera
authors.affiliation: Division of Global Public Health, Department of Medicine, University of California, San Diego, 9500 Gilman Drive, MC 0507, La Jolla, CA 92093-0507, USA. Electronic address: kbrouwer@ucsd.edu.
authors.forename: Kimberly C
authors.initials: KC
authors.lastname: Brouwer
mesh_terms: D000328:Adult; D003625:Data Collection; D055030:Drug Users / Q000706:statistics & numerical data*; D005260:Female; D005500:Follow-Up Studies; D015658:HIV Infections / Q000453:epidemiology* / Q000635:transmission; D006297:Health Services Accessibility / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D008800:Mexico / Q000453:epidemiology; D016485:Needle Sharing / Q000706:statistics & numerical data; D015995:Prevalence; D012309:Risk-Taking; D011477:Sex Work / Q000706:statistics & numerical data; D012725:Sexual Behavior / Q000706:statistics & numerical data*; D012749:Sexually Transmitted Diseases / Q000453:epidemiology; D015819:Substance Abuse, Intravenous / Q000453:epidemiology*; D014195:Travel / Q000706:statistics & numerical data
keywords: Female sex work; HIV; Injection drug use; Mobility; Tijuana; Transmission hotspot