HIV Case Finding and Genetic Transmission Networks among MSM in Tijuana, Mexico


Funding Source: NIH R01 DA037811-01

PIs: Thomas L. Patterson (lead PI); Steffanie A. Strathdee; Shirley J. Semple; Heather A. Pines

Project Period: July 2014- June 2019

The goal of this project is to compare the effectiveness of two methods (Respondent-Driven Sampling [RDS] versus Venue-Based [VB] recruitment) for identifying previously undiagnosed HIV+ cases among men who have sex with men (MSM) in Tijuana, Mexico. We will also use self-reported sexual networks, venue-based networks, and viral genetic networks (inferred by analysis of HIV-1 pol sequences from newly diagnosed cases) to identify missing connections (e.g., anonymous partners) in sexual transmission networks. In our MSM pilot study, HIV prevalence was 20.2%, and 88% of infected men were unaware of their HIV+ serostatus. Identifying previously undiagnosed HIV+ persons and linking them to care are critical steps in the HIV treatment cascade, particularly among MSM, who are disproportionately affected by HIV in Mexico.

 The aims of the study are:

  1. To compare the effectiveness of RDS versus VB recruitment (i.e., screening attendees of high-risk venues (e.g., bars, saunas, sex clubs) in Tijuana) as methods for finding previously undiagnosed HIV+ cases.
  2. To determine the extent to which sexual networks generated through RDS and venue affiliation networks map onto inferred viral genetic networks at baseline and one-year follow-up.
  3. To examine the relationship between HIV case finding methods (RDS and VB recruitment) and (a) linkage to and retention in HIV care as well as psychosocial and environmental determinants of these outcomes and (b) sexual network stability assessed at one-year follow-up.

    We will pursue both methods of HIV case finding continuously and simultaneously until 200 previously undiagnosed HIV+ cases are identified via each method. Participants will complete surveys using computer-assisted personal-interviewing (CAPI) technology with the assistance of an interviewer. Baseline surveys will gather demographic, behavioral, and psychosocial data, sexual network data, as well as data on venue characteristics. Blood samples will also be collected at baseline for HIV-1 pol sequencing. At one-year follow-up visits, participants will complete a shorter version of the survey (omitting demographics and lifetime behavior questions) that includes questions pertaining to HIV care. The one-year timeframe will allow us to identify how many HIV+ MSM link to care, the barriers they encounter in attempting to link to care, and how stable their sexual networks remain following HIV diagnosis.