title: HIV Transmission Networks in the San Diego-Tijuana Border Region.
abstract: BACKGROUND
  HIV sequence data can be used to reconstruct local transmission networks. Along international borders, like the San Diego-Tijuana region, understanding the dynamics of HIV transmission across reported risks, racial/ethnic groups, and geography can help direct effective prevention efforts on both sides of the border.
  
  
  METHODS
  We gathered sociodemographic, geographic, clinical, and viral sequence data from HIV infected individuals participating in ten studies in the San Diego-Tijuana border region. Phylogenetic and network analysis was performed to infer putative relationships between HIV sequences. Correlates of identified clusters were evaluated and spatiotemporal relationships were explored using Bayesian phylogeographic analysis.
  
  
  RESULTS
  After quality filtering, 843 HIV sequences with associated demographic data and 263 background sequences from the region were analyzed, and 138 clusters were inferred (2-23 individuals). Overall, the rate of clustering did not differ by ethnicity, residence, or sex, but bisexuals were less likely to cluster than heterosexuals or men who have sex with men (p = 0.043), and individuals identifying as white (p ≤ 0.01) were more likely to cluster than other races. Clustering individuals were also 3.5 years younger than non-clustering individuals (p < 0.001). Although the sampled San Diego and Tijuana epidemics were phylogenetically compartmentalized, five clusters contained individuals residing on both sides of the border.
  
  
  CONCLUSIONS
  This study sampled ~ 7% of HIV infected individuals in the border region, and although the sampled networks on each side of the border were largely separate, there was evidence of persistent bidirectional cross-border transmissions that linked risk groups, thus highlighting the importance of the border region as a "melting pot" of risk groups.
  
  
  BACKGROUND
  NIH, VA, and Pendleton Foundation.
authors.affiliation: Division of Infectious Diseases, University of California San Diego, #8208 200 W. Arbor St. San Diego, CA 92103, United States ; Division of Infectious Diseases, San Diego Veterans Affairs Medical Center, 3350 La Jolla Village Drive, San Diego, CA 92161, United States.
authors.forename: Sanjay R
authors.initials: SR
authors.lastname: Mehta
authors.affiliation: Division of Infectious Diseases, University of California San Diego, #8208 200 W. Arbor St. San Diego, CA 92103, United States.
authors.forename: Joel O
authors.initials: JO
authors.lastname: Wertheim
authors.affiliation: Division of Global Public Health, University of California San Diego, #0507, La Jolla, CA 92093, United States.
authors.forename: Kimberly C
authors.initials: KC
authors.lastname: Brouwer
authors.affiliation: School of Community Health Sciences, University of Nevada Reno, Lombardi Building, 203, MS 0274, Reno, NV 89557, United States.
authors.forename: Karla D
authors.initials: KD
authors.lastname: Wagner
authors.affiliation: Division of Infectious Diseases, University of California San Diego, #8208 200 W. Arbor St. San Diego, CA 92103, United States.
authors.forename: Antoine
authors.initials: A
authors.lastname: Chaillon
authors.affiliation: Division of Global Public Health, University of California San Diego, #0507, La Jolla, CA 92093, United States.
authors.forename: Steffanie
authors.initials: S
authors.lastname: Strathdee
authors.affiliation: Department of Psychiatry, University of California San Diego #0680, La Jolla, CA 92093, United States.
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Patterson
authors.affiliation: El Colegio de la Frontera Norte, San Antonio del Mar, Baja California, Mexico.
authors.forename: Maria G
authors.initials: MG
authors.lastname: Rangel
authors.affiliation: Division of Infectious Diseases, University of California San Diego, #8208 200 W. Arbor St. San Diego, CA 92103, United States.
authors.forename: Mlenka
authors.initials: M
authors.lastname: Vargas
authors.affiliation: Division of Infectious Diseases, University of California San Diego, #8208 200 W. Arbor St. San Diego, CA 92103, United States.
authors.forename: Ben
authors.initials: B
authors.lastname: Murrell
authors.affiliation: Division of Global Public Health, University of California San Diego, #0507, La Jolla, CA 92093, United States.
authors.forename: Richard
authors.initials: R
authors.lastname: Garfein
authors.affiliation: Division of Infectious Diseases, University of California San Diego, #8208 200 W. Arbor St. San Diego, CA 92103, United States.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Little
authors.affiliation: Division of Infectious Diseases, University of California San Diego, #8208 200 W. Arbor St. San Diego, CA 92103, United States ; Division of Infectious Diseases, San Diego Veterans Affairs Medical Center, 3350 La Jolla Village Drive, San Diego, CA 92161, United States.
authors.forename: Davey M
authors.initials: DM
authors.lastname: Smith
mesh_terms: D000328:Adult; D001499:Bayes Theorem; D002140:California / Q000453:epidemiology; D016000:Cluster Analysis; D024882:Drug Resistance, Viral / Q000235:genetics; D004641:Emigration and Immigration; D005260:Female; D016679:Genome, Viral; D015658:HIV Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000635:transmission* / Q000821:virology; D015497:HIV-1 / Q000145:classification / Q000187:drug effects / Q000235:genetics; D006801:Humans; D008297:Male; D008800:Mexico / Q000453:epidemiology; D008875:Middle Aged; D009154:Mutation; D010802:Phylogeny; D011159:Population Surveillance; D017422:Sequence Analysis, DNA; D012959:Socioeconomic Factors; D055815:Young Adult
keywords: HIV; International border; Mexico; Phylogeography; Transmission network