Prevalence and correlates of HIV among men who have sex with men in Tijuana, Mexico

Interpersonal and Community-Level Influences Across the PrEP Cascade Among Young Adult Latinx Men who Have Sex with Men Living in a US-Mexico Border Region: A Qualitative Study

Latinx men who have sex with men (MSM) are an at-risk population for new HIV diagnoses. Pre-exposure prophylaxis (PrEP) is a suite of biomedical approaches to prevent HIV infection. Latinx MSM are less likely to take PrEP compared to non-Latinx White MSM. This qualitative study identified interpersonal- and community-level barriers and facilitators of PrEP among young adult Latinx MSM. Using stratified purposeful sampling, 27 Latinx men, ages 19-29 years and living in a US-Mexico border region, completed self-report demographic surveys and participated in semi-structured in-depth interviews assessing barriers and facilitators to PrEP. Directed content analysis was used to identify both a priori and emerging themes. Most participants reported that other people, including peers, friends, partners, and health care providers were both supportive and discouraging of PrEP use. Participants' intersectional identities as members of both Latinx and LGBTQ+ (Lesbian, Gay, Bisexual, Transgender, Queer) communities both hindered and facilitated PrEP use.

Patient sexuality disclosure experience and associations with clinical sexual health outcomes among HIV-negative men who have sex with men in Mexico

Many men who have sex with men (MSM) do not disclose their sexuality to their healthcare provider, despite potential health benefits. Data from the 2017 Encuesta de Sexo Entre Hombres online survey of 13,277 HIV-negative or unknown status MSM in Mexico were used to explore MSM patients' sexuality disclosure experience on sexual health outcomes using multivariable Poisson models with robust variance estimation to estimate adjusted prevalence ratios (aPR). Sexual health outcomes included Hepatitis B (HepB) and human papillomavirus (HPV) vaccination, and lifetime and past year HIV testing. Overall, 53.9% (n/N) disclosed their sexuality to their healthcare provider, and of those 6.4%, 62.9%, and 30.7% reported a negative, neutral, or positive disclosure experience, respectively. In comparison to no disclosure, neutral and positive disclosure experiences were associated with HepB vaccination (aPR[95% Confidence Interval (95% CI)] = 1.17[1.09, 1.25], p < 0.001; aPR[95% CI] = 1.35[1.25, 1.46], p < 0.001, respectively) and positive disclosure experiences were associated with HPV vaccination (aPR[95% CI] = 1.46[1.24, 1.71], p < 0.001). Those who disclosed their sexual behavior were more likely than those who did not disclose their sexual behavior to have received an HIV test in their lifetime (negative: aPR[95% CI] = 1.51[1.43, 1.60], p < 0.001; neutral: aPR[95% CI] = 1.61[1.56, 1.66], p < 0.001; positive: aPR[95% CI] = 1.64[1.58, 1.69], p < 0.001) and an HIV test in the past year (negative: aPR[95% CI] = 1.89[1.70, 2.10], p < 0.001; neutral: aPR[95% CI] = 2.09[1.98, 2.20], p < 0.001; positive: aPR[95% CI] = 2.24[2.12, 2.37], p < 0.001). There is a need to implement trainings for healthcare providers that focus on sexual health risk assessments and creating a space that encourages MSM patients and healthcare providers to discuss sexual health.

Metodología de una encuesta por internet para hombres que tienen sexo con hombres en México

OBJETIVO

Describir el diseño, implementación y el perfil de los participantes de la Encuesta de Sexo Entre Hombres (ES Entre Hombres). Material y métodos. ES Entre Hombres es una encuesta en línea no probabilística aplicada a nivel nacional a hombres de 18 años o más, que tienen sexo con hombres (HSH) y que usan internet. La población de estudio se reclutó a través de publicidad en diversos sitios de encuentro en línea y los cuestionarios se autoaplicaron con SurveyGizmo.

RESULTADOS

Durante 11 semanas se registró un total de 15 875 autoaplicaciones elegibles y completas de las 32 entidades del país. La mayoría de los participantes fueron jóvenes (<29 años; 65.7%) y personas que acceden a internet diariamente (94.3%). Conclusión. Las encuestas realizadas por internet para poblaciones como los HSH representan un método costoefectivo de estudio poblacional, ya que tienen el potencial de ahorrar recursos y alcanzar muestras grandes, lo que a la vez facilita la cobertura geográfica a un bajo costo.

Overlapping Key Populations and HIV Transmission in Tijuana, Mexico: A Modelling Analysis of Epidemic Drivers

Tijuana, Mexico, has a concentrated HIV epidemic among overlapping key populations (KPs) including people who inject drugs (PWID), female sex workers (FSW), their male clients, and men who have sex with men (MSM). We developed a dynamic HIV transmission model among these KPs to determine the extent to which their unmet prevention and treatment needs is driving HIV transmission. Over 2020-2029 we estimated the proportion of new infections acquired in each KP, and the proportion due to their unprotected risk behaviours. We estimate that 43.7% and 55.3% of new infections are among MSM and PWID, respectively, with FSW and their clients making-up < 10% of new infections. Projections suggest 93.8% of new infections over 2020-2029 will be due to unprotected sex between MSM or unsafe injecting drug use. Prioritizing interventions addressing sexual and injecting risks among MSM and PWID are critical to controlling HIV in Tijuana.

The Prevalence of HIV Among Men Who Have Sex With Men (MSM) and Young MSM in Latin America and the Caribbean: A Systematic Review

Young men who have sex with men (YMSM) under 25 years old are among the few populations with increasing numbers of new HIV infections in parts of the world where HIV incidence is declining overall. In this systematic review, we synthesize the literature on HIV prevalence among MSM in Latin America and the Caribbean focusing on YMSM. Results were stratified according to study population sampling method used (probability and non-probability based). Forty-seven studies from 17 countries were published in the last 10 years. Among studies using probability-based sampling method (N = 21), HIV prevalence among MSM ranged from 1.2 to 32.6%. HIV prevalence tended to increase over time in studies sampling at different time points. HIV prevalence among YMSM exceeded 5.0% in more than a half of studies (51%; N = 22/43). Our review corroborates the high and potentially rising incidence of HIV among YMSM and characterizes the region's greatest challenge to ending the epidemic.

Low socioeconomic status is associated with self-reported HIV positive status among young MSM in Brazil and Peru

BACKGROUND

Despite efforts to stop HIV epidemic in Latin America, new HIV cases continue to increase in the region especially among young MSM (YMSM). This study aims to assess if sociodemographic characteristics are associated with self-reported HIV positive status among YMSM from three Latin American countries.

METHODS

Cross-sectional web-based survey advertised on dating apps (Grindr and Hornet) and Facebook in Brazil, Mexico and Peru. For this analysis, we included YMSM aged 18-24 years who self-reported their HIV status. We used multivariable logistic regression models for each country separately to verify if sociodemographic characteristics (race, education and income) were associated with HIV self-reported status after adjusting for behavior characteristics (sexual attraction and steady partner).

RESULTS

Among 43,687 MSM who initiated the questionnaire, 27,318 (62.5%) reported their HIV status; 7001 (25.6%) of whom were YMSM. Most YMSM (83.4%) reported an HIV test in the past year, and 15.7% reported an HIV positive status in Peru, 8.4% in Mexico and 7.7% in Brazil. In adjusted models, low-income was associated with higher odds of self-reported HIV positive status in Brazil (aOR = 1.33, 95%CI: 1.01-1.75) and Peru (aOR = 1.56, 95%CI: 1.02-2.40), but not in Mexico. Lower education was associated with higher odds of self-reported HIV positive status only in Brazil (aOR = 1.35, 95%CI: 1.05-1.75).

CONCLUSIONS

In this large, cross-country study, self-reported HIV positive status among YMSM was high. Lower socioeconomic status was associated with higher odds of self-reported HIV positive status in Brazil and Peru. There is an urgent need for HIV prevention interventions targeting YMSM, and efforts to address low-income YMSM are especially needed in Peru and Brazil.

Prevalence of bacterial sexually transmitted infections and coinfection with HIV among men who have sex with men and transgender women in Tijuana, Mexico

We estimated the prevalence of syphilis and Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) infections, as well as human immunodeficiency virus (HIV) coinfection among cisgender men who have sex with cisgender men (MSM) and transgender women (TW) in Tijuana, Mexico. MSM and TW (N = 212) recruited via respondent-driven and venue-based sampling for HIV testing underwent sexually transmitted infection (STI) testing and completed interviewer-administered surveys in this study (2017-2018). Treponemal rapid tests were used at the point-of-care with positives undergoing confirmatory testing following the reverse syphilis-testing algorithm. Nucleic acid amplification testing of urine and swabs (rectal and pharyngeal) was used to detect CT/NG at three anatomic sites. Chi-squared tests were used to compare STI prevalence by HIV status. Sexually transmitted infection prevalence was 39.6% overall but higher for newly diagnosed HIV-positive (55.7%; N = 88) than HIV-negative (28.2%; N = 124) participants (p-value < 0.0001). Among newly diagnosed HIV-positive participants, the prevalence of syphilis was 35.2% (31/88), CT infection was 27.3% (24/88; nine urethral; 16 rectal; four pharyngeal), and NG infection was 26.1% (23/88; six urethral; 19 rectal; nine pharyngeal). Among HIV-negative participants, the prevalence of syphilis was 12.1% (15/124), CT infection was 13.7% (17/124; seven urethral; nine rectal; two pharyngeal), and NG infection was 9.7% (12/124; three urethral; seven rectal; seven pharyngeal). Over 60% of all CT (25/41) and NG (26/35) infections in the full sample occurred extragenitally in the absence of urethral infections, and over 80% of rectal (30/37) and pharyngeal (16/18) infections were asymptomatic. The high prevalence of syphilis, CT, and NG infections among MSM and TW in Tijuana suggests STI screening that includes extragenital tests, particularly at HIV diagnosis, may help curb HIV/STI transmission.

Developing HIV assisted partner notification services tailored to Mexican key populations: a qualitative approach

Background

Assisted partner notification services (APNS) may increase HIV testing, early diagnosis, and treatment, but they are not formally implemented in Mexico, where the HIV epidemic is concentrated in men who have sex with men (MSM) and transwomen (TW). This study aimed to explore the awareness of and need for HIV partner notification, as well as to outline potential strategies for APNS based on identified barriers and facilitators.

Methods

We conducted semi-structured interviews to explore partner notification with MSM, TW, and counselors. Afterwards, brainstorm sessions were carried out to produce strategies for implementing APNS.

Results

Most participants reported experiences with informal partner notification and serostatus disclosure, but not with APNS. Only one counselor indicated assisting notification systematically. The main barriers for notifying or disclosing mentioned by both MSM and TW included fear of (violent) reactions, discrimination and lacking contact information of casual partners. Participants thought it was easier to inform a formal partner, conditional of being well informed about HIV. Given current stigma and lack of awareness, it was suggested that APNS should be preceded by HIV awareness efforts, and be provided by counselors or peers to mitigate potential rejection or violent reactions.

Conclusions

While APNS are not formally implemented in Mexico, all participants supported the service, indicating that APNS could potentially enhance early HIV diagnosis in Mexico. Strategies to implement such services need to be flexible addressing the individual needs of participants, guaranteeing the safety of more vulnerable participants.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-10612-3.

A comparison of the effectiveness of respondent-driven and venue-based sampling for identifying undiagnosed HIV infection among cisgender men who have sex with men and transgender women in Tijuana, Mexico

BACKGROUND

Efforts to increase HIV testing, diagnosis and care are critical to curbing HIV epidemics among cisgender men who have sex with men (MSM) and transgender women (TW) in low- and middle-income countries (LMIC). We compared the effectiveness of respondent-driven sampling (RDS) and venue-based sampling (VBS) for identifying previously undiagnosed HIV infection among MSM and TW in Tijuana, Mexico.

METHODS

Between March 2015 and December 2018, we conducted RDS within the social networks of MSM and TW and VBS at venues frequented by MSM and TW to socialize and meet sexual partners. Those reached by RDS/VBS who reported at least 18 years of age, anal sex with MSM or TW, and no previous HIV diagnosis were eligible for HIV testing.

RESULTS

Of those screened following recruitment via RDS (N = 1232; 98.6% MSM; 1.3% TW), 60.8% (749/1232) were eligible for HIV testing and 97.5% (730/749) were tested for HIV infection, which led to the identification of 36 newly diagnosed HIV infections (4.9%). Of those screened following recruitment via VBS (N = 2560; 95.2% MSM; 4.6% TW), 56.5% (1446/2560) were eligible for HIV testing and 92.8% (1342/1446) were tested for HIV infection, which led to the identification of 82 newly diagnosed HIV infections (6.1%). The proportion of new HIV diagnoses did not differ by recruitment method (ratio = 0.81, 95% confidence interval: 0.55 to 1.18). Compared to those recruited via RDS, those tested following recruitment via VBS were younger, more likely to identify as gay, and more likely to identify as TW. Compared to those recruited via VBS, those newly diagnosed with HIV infection following recruitment via RDS reported higher levels of internalized stigma and were more likely to report injection drug use and a history of deportation from the United States.

CONCLUSIONS

Despite RDS and VBS being equally effective for identifying undiagnosed HIV infection, each recruitment method reached different subgroups of MSM and TW in Tijuana. Our findings suggest that there may be benefits to using both RDS and VBS to increase the identification of previously undiagnosed HIV infection and ultimately support HIV care engagement among MSM and TW in Mexico and other similar LMIC.

Incidence and time-varying predictors of HIV and sexually transmitted infections among male sex workers in Mexico City

Background

Male sex workers are at high-risk for acquisition of sexually transmitted infections (STIs), including human immunodeficiency virus (HIV). We quantified incidence rates of STIs and identified their time-varying predictors among male sex workers in Mexico City.

Methods

From January 2012 to May 2014, male sex workers recruited from the largest HIV clinic and community sites in Mexico City were tested for chlamydia, gonorrhea, syphilis, hepatitis, and HIV at baseline, 6-months, and 12-months. Incidence rates with 95% bootstrapped confidence limits were calculated. We examined potential time-varying predictors using generalized estimating equations for a population averaged model.

Results

Among 227 male sex workers, median age was 24 and baseline HIV prevalence was 32%. Incidence rates (per 100 person-years) were as follows: HIV [5.23; 95% confidence interval (CI): 2.15–10.31], chlamydia (5.15; 95% CI: 2.58–9.34), gonorrhea (3.93; 95% CI: 1.88–7.83), syphilis (13.04; 95% CI: 8.24–19.94), hepatitis B (2.11; 95% CI: 0.53–4.89), hepatitis C (0.95; 95% CI: 0.00–3.16), any STI except HIV (30.99; 95% CI: 21.73–40.26), and any STI including HIV (50.08; 95% CI: 37.60–62.55). In the multivariable-adjusted model, incident STI (excluding HIV) were lower among those who reported consistently using condoms during anal and vaginal intercourse (odds ratio = 0.03, 95% CI: 0.00–0.68) compared to those who reported inconsistently using condoms during anal and vaginal intercourse.

Conclusions

Incidence of STIs is high among male sex workers in Mexico City. Consistent condom use is an important protective factor for STIs, and should be an important component of interventions to prevent incident infections.

Epidemiological and Molecular Characteristics of HIV-1 Infection in a Sample of Men Who Have Sex With Men in Brazil: Phylogeography of Major Subtype B and F1 Transmission Clusters

This study describes human immunodeficiency virus 1 (HIV-1) prevalence, associated factors, viral genetic diversity, transmitted drug resistance (TDR), and acquired drug resistance mutations (DRM) among a population of 522 men who have sex with men (MSM) recruited by the respondent-driven sampling (RDS) method, in Goiânia city, the capital of the State of Goiás, Central-Western Brazil. All serum samples were tested using a four-generation enzyme-linked immunosorbent assay (ELISA), and reactive samples were confirmed by immunoblotting. Plasma RNA or proviral DNA was extracted, and partial polymerase (pol) gene including the protease/reverse transcriptase (PR/RT) region was amplified and sequenced. HIV-1 subtypes were identified by phylogenetic inference and by bootscan analysis. The time and location of the ancestral strains that originated the transmission clusters were estimated by a Bayesian phylogeographic approach. TDR and DRM were identified using the Stanford databases. Overall, HIV-1 prevalence was 17.6% (95% CI: 12.6–23.5). Self-declared black skin color, receptive anal intercourse, sex with drug user partner, and history of sexually transmitted infections were factors associated with HIV-1 infection. Of 105 HIV-1-positive samples, 78 (74.3%) were sequenced and subtyped as B (65.4%), F1 (20.5%), C (3.8%), and BF1 (10.3%). Most HIV-1 subtype B sequences (67%; 34 out of 51) branched within 12 monophyletic clusters of variable sizes, which probably arose in the State of Goiás between the 1980s and 2010s. Most subtype F1 sequences (n = 14, 88%) branched in a single monophyletic cluster that probably arose in Goiás around the late 1990s. Among 78 samples sequenced, three were from patients under antiretroviral therapy (ART); two presented DRM. Among 75 ART-naïve patients, TDR was identified in 13 (17.3%; CI 95%: 9.6–27.8). Resistance mutations to non-nucleoside reverse transcriptase inhibitors (NNRTI) predominated (14.7%), followed by nucleoside reverse transcriptase inhibitor (NRTI) mutations (5.3%) and protease inhibitor (PI) mutations (1.3%). This study shows a high prevalence of HIV-1 associated with sexual risk behaviors, high rate of TDR, and high genetic diversity driven by the local expansion of different subtype B and F1 strains. These findings can contribute to the understanding about the dissemination and epidemiological and molecular characteristics of HIV-1 among the population of MSM living away from the epicenter of epidemics in Brazil.

Sex differences in the multilevel determinants of injection risk behaviours among people who inject drugs in Tijuana, Mexico

INTRODUCTION AND AIMS

HIV and hepatitis C virus transmission among people who inject drugs (PWID) is fuelled by personal and environmental factors that vary by sex. We studied PWID in Mexico to identify sex differences in multilevel determinants of injection risk.

DESIGN AND METHODS

From 2011 to 2013, 734 PWID (female: 277, male: 457) were enrolled into an observational cohort study in Tijuana. Participants completed interviews on injection and sexual risks. Utilising baseline data, we conducted multiple generalised linear models stratified by sex to identify factors associated with injection risk scores (e.g. frequency of injection risk behaviours).

RESULTS

For both sexes, difficult access to sterile syringes was associated with elevated injection risk (b = 1.24, 95% confidence interval [CI] 1.16-1.33), using syringes from a safe source (e.g. needle exchange programs) was associated with lower injection risk (b = 0.87, 95% CI 0.82-0.94), and for every one-unit increase in safe injection self-efficacy we observed a 20% decrease in injection risk (b = 0.80, 95% CI 0.76-0.84). Females had a higher safe injection self-efficacy score compared to males (median 2.83, interquartile range 2.2-3 vs. median 2.83, interquartile range 2-3; P = 0.01). Among females, incarceration (b = 1.22, 95% CI 1.09-1.36) and police confiscation of syringes in the past 6 months (b = 1.16, 95% CI 1.01-1.33) were associated with elevated injection risk. Among males, sex work (b = 1.16, 95% CI 1.04-1.30) and polysubstance use in the past 6 months (b = 1.22, 95% CI 1.13-1.31) were associated with elevated injection risk.

DISCUSSION AND CONCLUSIONS

Interventions to reduce HIV and hepatitis C virus transmission among PWID in Tijuana should be sex-specific and consider multilevel determinants of injection risk to create safer drug use environments.

Recent HIV Infection among men who have sex with men and transgender women in Tijuana

OBJECTIVE To characterize recent HIV infections among newly diagnosed men who have sex with men and transgender women in Tijuana. METHODS Limiting Antigen (LAg)-Avidity testing was performed to detect recent HIV infection within a cohort of newly-diagnosed men who have sex with men and transgender women in Tijuana. Logistic regression was used to determine characteristics associated with recent infection. A partial transmission network was inferred using HIV-1 pol sequences. Tamura-Nei 93 genetic distances were measured between all pairs of sequences, and the network was constructed by inferring putative transmission links (genetic distances ≤ 1.5%). We assessed whether recent infection was associated with clustering within the inferred network. RESULTS Recent infection was detected in 11% (22/194) of newly-diagnosed participants. Out of the participants with sequence data, 60% (9/15) with recent infection clustered compared with 31% (43/139) with chronic infection. Two recent infections belonged to the same cluster. In adjusted analyses, recent infection was associated with years of residence in Tijuana (OR = 1.5; 95%CI 1.01-1.09), cocaine use (past month) (OR = 8.50; 95%CI 1.99-28.17), and ever experiencing sexual abuse (OR = 2.85; 95%CI 1.03-7.85). DISCUSSION A total of 11% of men newly diagnosed with HIV who have sex with men and transgender women in Tijuana were recently infected. The general lack of clustering between participants with recent infection suggests continued onward HIV transmission rather than an outbreak within a particular cluster.

Methamphetamine Use and Sexual Risk Behaviors among Men Who Have Sex With Men in a Mexico-US Border City

BACKGROUND AND OBJECTIVES

Methamphetamine (meth) use and its related risk behaviors for HIV among men who have sex with men (MSM) are a public health concern across the Mexico-US border. This study aims to contribute to the limited literature of meth use and sexual risk behaviors among Latino MSM on the Mexico-US border.

METHODS

Data were drawn from the Meth Pilot Study (2014-2015) among men who use meth (n = 100). Descriptive statistics and bivariate analysis comparing MSM to non-MSM were conducted using Pearson's χ2 test, Fisher's exact tests, and Mann-Whitney U test; all tests were conducted using SPSS v.25.

RESULTS

Most participants obtained meth in El Paso, Texas (87.2%), used meth orally (65.2%) or smoked (78.3%), and the most common reason for initiation was curiosity. Significant differences (P < .05) in meth use behaviors and sexual risk behaviors between MSM and non-MSM who used meth included: median number of sex partners (7 vs 3), being penetrated anally by last sexual partner (31.6% vs 1.4%), and engaging in transactional sex ever (63.2% vs 9.6%) and past 12 months (52.6% vs 6.8%). Finally, rates of HIV positivity were higher among MSM than non-MSM (10.5% vs 1.4%).

DISCUSSION AND CONCLUSIONS

Among men who use meth, MSM are engaging in higher HIV risk behaviors compared with non-MSM. Understanding these risks could help identify candidates for pre-exposure prophylaxis (PrEP) and evidence-based substance use disorder treatment options.

SCIENTIFIC SIGNIFICANCE

This study reveals that Latino MSM who use meth is a high-risk group for HIV and a need for tailored interventions. (Am J Addict 2020;29:111-119).

HIV Prevention Method Preferences Within Sexual Partnerships Reported by HIV-Negative MSM and TW in Tijuana, Mexico

To assess the potential for decreased condom use as pre-exposure prophylaxis (PrEP) is scaled-up in Latin America, we examined HIV prevention method preferences (neither PrEP nor condoms, condoms only, PrEP only, or PrEP with condoms) within 1302 sexual partnerships reported by 397 HIV-negative men who have sex with men (MSM) and transgender women (TW) in Tijuana, Mexico. Using PrEP with condoms (56%) was preferred to using condoms only (24%), using PrEP only (17%), and using neither PrEP nor condoms (3%). Compared to using condoms only, using PrEP only was preferred within primary (adjusted odds ratio [AOR] = 4.13, 95% confidence interval [CI] 1.92, 8.90) and condomless sex practicing (AOR = 6.97, 95% CI 3.92, 12.40) partnerships, suggesting PrEP use may not displace condom use among MSM and TW in Tijuana and other similar settings.

Stigma and Web-Based Sex Seeking Among Men Who Have Sex With Men and Transgender Women in Tijuana, Mexico: Cross-Sectional Study

BACKGROUND

Stigma toward sexual and gender minorities is an important structural driver of HIV epidemics among men who have sex with men (MSM) and transgender women (TW) globally. Sex-seeking websites and apps are popular among MSM and TW. Interventions delivered via Web-based sex-seeking platforms may be particularly effective for engaging MSM and TW in HIV prevention and treatment services in settings with widespread stigma toward these vulnerable populations.

OBJECTIVE

To assess the potential utility of this approach, the objectives of our study were to determine the prevalence of Web-based sex seeking and examine the effect of factors that shape or are influenced by stigma toward sexual and gender minorities on Web-based sex seeking among MSM and TW in Tijuana, Mexico.

METHODS

From 2015 to 2018, 529 MSM and 32 TW were recruited through venue-based and respondent-driven sampling. Interviewer-administered surveys collected information on Web-based sex seeking (past 4 months) and factors that shape or are influenced by stigma toward sexual and gender minorities (among MSM and TW: traditional machismo, internalized stigma related to same-sex sexual behavior or gender identity, and outness related to same-sex sexual behavior or gender identity; among MSM only: sexual orientation and history of discrimination related to same-sex sexual behavior). A total of 5 separate multivariable logistic regression models were used to examine the effect of each stigma measure on Web-based sex seeking.

RESULTS

A total of 29.4% (165/561) of our sample reported seeking sex partners on the Web. Web-based sex seeking was negatively associated with greater endorsement of traditional machismo values (adjusted odds ratio [AOR] 0.36, 95% CI 0.19 to 0.69) and greater levels of internalized stigma (AOR 0.96, 95% CI 0.94 to 0.99). Web-based sex seeking was positively associated with identifying as gay (AOR 2.13, 95% CI 1.36 to 3.33), greater outness (AOR 1.17, 95% CI 1.06 to 1.28), and a history of discrimination (AOR 1.83, 95% CI 1.08 to 3.08).

CONCLUSIONS

Web-based sex-seeking is relatively common among MSM and TW in Tijuana, suggesting that it may be feasible to leverage Web-based sex-seeking platforms to engage these vulnerable populations in HIV prevention and treatment services. However, HIV interventions delivered through Web-based sex-seeking platforms may have limited reach among those most affected by stigma toward sexual and gender minorities (ie, those who express greater endorsement of traditional machismo values, greater levels of internalized stigma, lesser outness, and nongay identification), given that within our sample they were least likely to seek sex on the Web.

Perceived Need and Acceptability of a Community-Based Peer Navigator Model to Engage Key Populations in HIV Care in Tijuana, Mexico

INTRODUCTION

Prior work found <4% of key populations living with HIV (KPLWH) in Tijuana, Mexico, were on antiretroviral therapy (ART). The goal of this pilot study was to examine community stakeholders' perceived need and acceptability of a peer-navigator program to improve ART coverage.

METHODS

We held a community forum and measured perspectives of key stakeholders in local organizations that serve KPLWH using online surveys, and in-depth interviews (with select key informants).

RESULTS

Univariate descriptive statistics and emergent thematic analysis illustrated that there was general consensus that the program could improve ART coverage for KPLWH by helping to overcome geographic, transportation, and sociostructural barriers to HIV care. Police harassment, mobility, and non-HIV comorbidities were identified as challenges the program would need to navigate.

CONCLUSIONS

Community stakeholders expressed perceived need and acceptability of a program to improve HIV care outcomes among KPLWH in Tijuana. The program should address the challenges identified by community stakeholders.

Perceived barriers to pre-exposure prophylaxis use among HIV-negative men who have sex with men in Tijuana, Mexico: A latent class analysis

BACKGROUND

Given the slow uptake of PrEP among cisgender men who have sex with men (MSM) in high-income countries, efforts to roll-out PrEP in low- and middle-income countries (LMIC) should address barriers to PrEP use to facilitate its more rapid uptake. To inform PrEP programs in LMIC, we examined patterns of perceived barriers to PrEP use among HIV-negative MSM in Tijuana, Mexico.

METHODS

From 03/2016-09/2017, 364 MSM completed interviewer-administered surveys assessing perceived barriers to PrEP use across 4 domains: PrEP attribute, individual, interpersonal, and structural. Latent class analysis was performed to identify distinct classes with respect to perceived barriers to PrEP use. Multinomial logistic regression was used to identify factors associated with class membership.

RESULTS

We identified three classes characterized by (1) high levels of perceived barriers across domains (12%), (2) low levels of perceived barriers across domains (43%), and (3) perceived PrEP attribute barriers (i.e., side-effects and cost) (45%). Membership in the high level of perceived barriers class (vs. the low level of perceived barriers class) was positively associated with having a history of incarceration (AOR: 2.44; 95% CI: 1.04, 5.73) and negatively associated with more social support (AOR: 0.99; 95% CI: 0.98, 1.00). Membership in the perceived PrEP attribute barriers class was positively associated with having seen a healthcare provider in the past year (AOR: 2.78; 95% CI: 1.41, 5.45) and negatively associated with having any HIV-positive or status unknown partners (AOR: 0.56; 95% CI: 0.31, 1.01).

CONCLUSIONS

Since most participants were in either the low level of perceived barriers class or the perceived PrEP attribute barriers class, future PrEP uptake may be high among MSM in Tijuana. However, these findings suggest that achieving sufficient PrEP uptake and adherence among MSM in Tijuana may require a range of comprehensive HIV prevention interventions.

CAM Practices and Treatment Adherence Among Key Subpopulations of HIV+ Latinos Receiving Care in the San Diego-Tijuana Border Region: A Latent Class Analysis

Latinos living in the United States-Mexico border region bear a disproportionate HIV/AIDS burden compared to individuals living in the interior of both nations and face a constellation of barriers that determine their ability to access and adhere to HIV care. Use of complementary and alternative medicine (CAM) may be associated with suboptimal treatment adherence. Sociodemographic factors, health practices, and social determinants of health unique to the border region may further contribute to health disparities that undermine care engagement and continuity. Improved understanding of HIV-positive Latino subgroups and their risk profiles can lead to more effective, targeted clinical and public health interventions. We undertook this study to identify and characterize distinct classes of HIV-positive Latinos in the San Diego-Tijuana border region, differentiated by HIV and border-related factors, utilizing latent class analysis. We investigated relationships between class membership and CAM utilization and self-reported antiretroviral therapy (ART) adherence. Five distinct classes were identified with unique demographic, HIV risk, and border mobility profiles. CAM was recently used by nearly half of each class, though there were significant differences in the proportion of CAM use by class ranging from 44.4 to 90.9%. As well, all classes were currently receiving ART at similarly high rates and ART adherence outcomes were not significantly different based on class. Findings highlight the significant use of CAM by all HIV-positive Latinos in the border region and imply the need for a research framework which appropriately acknowledges the heterogeneous nature of this population, such as intersectionality. Further research is recommended into understanding how patients integrate CAM into HIV treatment and the risks and benefits of incorporating CAM into HIV treatment.

Uptake of a Partner Notification Model for HIV Among Men Who Have Sex With Men and Transgender Women in Tijuana, Mexico

Undiagnosed HIV infection is common among men who have sex with men (MSM) and transgender women (TW) in Latin America. We examined uptake of a partner notification (PN) model among MSM and TW in Tijuana, Mexico. Forty-six HIV-positive MSM/TW enrolled as index patients, and reported 132 MSM/TW sexual partners for PN. Of notified partners (90/132), 39% declined eligibility screening or participation, 39% tested for HIV, and of those 28% were newly-diagnosed HIV-positive. Partners who were seen by the index patient more than once in the past 4 months and those who primarily had sex with the index patient in one of their homes were more likely to be notified via PN (76% vs. 50%; p = 0.01 and 86% vs. 64%, p = 0.02, respectively). Lower than expected PN uptake was associated with problems identifying index patients, obtaining reliable partner contact information, and engaging notified partners.

Sexualised drug taking among men who have sex with men: a systematic review

AIMS:

Sexualised drug taking is increasingly reported on national and international levels. We aim to review existing evidence of the relationship between recreational drug use (RDU) and sexual intercourse among men who have sex with men (MSM).

METHODS:

We reviewed published abstracts and full articles identified from Cochrane, MEDLINE and Embase databases from November 2010 to 2017. We included any existing studies investigating RDU in MSM and at least one of the following: high-risk sexual practices, sexually transmitted infections (STIs) or barriers to accessing specialist support.

RESULTS:

In total, 112 studies were included. Of them, 38 studies specifically reported the prevalence of chemsex-related drug use. Links with sexualised drug taking and high-risk sexual practices including condomless sex and group sex were reported by several studies. Recreational drug use in the sexual setting appears linked to the acquisition of STIs, including hepatitis C, syphilis and gonorrhoea. Reports of adverse mental health outcomes are increasingly described, with several studies documenting chemsex-related inpatient admission. A paucity of research addressing barriers to those accessing specialist drug support services was identified.

CONCLUSION:

This review demonstrates the complex interplay between recreational drug use, high-risk sexual practices and STIs. It identifies the description of adverse mental health outcomes in the chemsex setting, thus highlighting the need for a multidisciplinary approach across specialties in the management of those adversely affected. Finally, it illuminates the need for future research into perceived barriers of those who require access to support services to ensure timely and comprehensive support provision.

Evaluation of HIV, STI and CD4 results among voluntary attendees at the HIV/AIDS program of Mexico City

Objective:

To describe results of HIV, sexually transmitted diseases (STI) and CD4 counts at the HIV-specialized Condesa Clinic (CC) in Mexico City.

Materials and methods:

Individuals who requested voluntary counseling and testing at CC were studied. We identified antibodies against HIV, syphilis, hepatitis C, and hepatitis B HBsAg. CD4 cell counts and viral load of HIV positive individuals were also obtained. Late HIV infection diagnosis was established if CD4 counts were lower than 200 cells/μL.

Results:

Global seroprevalence of HIV, syphilis, HBsAg, and anti HCV markers was of 20.1, 6, 1 and 1, respectively. Men displayed higher seroprevalence of infection markers than women. Among men, HIV infection was related to age and with all STI markers. Late HIV diagnosis was 31.8%. The risk of late HIV diagnosis was higher among women and it increased as age increased.

Conclusions:

Differences between genders regarding HIV and STIs prevalence as well as risk factors for HIV infection and late HIV diagnosis were observed.

Predictors of injecting cessation among a cohort of people who inject drugs in Tijuana, Mexico

INTRODUCTION

Little is known about the cessation of injecting drug use (IDU) among people who inject drugs (PWID) in low and middle-income settings, where access to effective interventions for reducing drug use (e.g., opioid substitution treatment; OST), may be limited. We measured the incidence and identified predictors of IDU cessation among a cohort of PWID in Tijuana, Mexico.

METHODS

Data were drawn from 621 participants in Proyecto El Cuete IV, a prospective cohort of PWID recruited in 2011 and interviewed biannually to 2016. A multivariable Extended Cox model was constructed to identify socio-demographic, drug use, risk environment and health-related predictors of IDU cessation (no IDU for ≥six months).

RESULTS

141 participants (23%) reported at least one IDU cessation event during follow-up. The crude IDU cessation rate was 7.3 per 100 person-years (95% Confidence Interval [CI]: 6.2-8.7). IDU cessation was negatively associated with injecting at least daily on average and heroin/methamphetamine co-injection in the past six months, and positively associated with testing HIV positive at baseline, being on methadone maintenance therapy in the past six months, and recent arrest. Concern for personal safety was also independently associated with IDU cessation.

CONCLUSIONS

The rate of IDU cessation among PWID in Tijuana was low. These findings underscore the importance of expansion of services including OST to help reduce drug use and facilitate IDU cessation for those who wish to do so. In this setting, interventions addressing individual-level economic barriers as well as broader social and structural barriers to harm reduction services are integral.

HIV Prevalence and Risk Behaviors in Male to Female (MTF) Transgender Persons in Tijuana, Mexico

Compared to HIV research on men who have sex with men, less is known about the risks and vulnerabilities for HIV among Male to Female (MTF) transgender persons, particularly in different geographic regions like Mexico. In Tijuana, Mexico, a border city experiencing a dynamic HIV epidemic, no precedent data exists on the MTF transgender population. Our aims were to estimate HIV prevalence and examine the behaviors and characteristics of the population. We conducted a cross-sectional study of 100 MTF transgender persons recruited through time location sampling in 2012. Participants underwent interviewer-administered (paper and pen) surveys and rapid tests for HIV. Descriptive univariate analyses were conducted on various factors, including sociodemographics, substance use, accessing social services (requested vs. received), stigma, and sex behaviors. A total of 22% tested positive for HIV, a prevalence higher than other key populations at risk for HIV in Tijuana.

Correlates of condomless anal sex among men who have sex with men (MSM) in Tijuana, Mexico: The role of public sex venues

Condomless anal sex between male partners is the primary risk factor for HIV transmission among men who have sex with men (MSM). Correlates of condomless anal sex have been well-studied in developed countries, but they have received less attention in lower-to-middle income countries (LMIC), where MSM are often subject to stigma, discrimination, intolerance, and even the criminalization of same sex behavior. In Mexico, a LMIC where traditional views on homosexuality are common, HIV prevalence among MSM is high (16.9%), yet little research has been conducted on the correlates of condomless anal sex in this high-risk population. The present study examined correlates of condomless anal sex among 201 MSM recruited in Tijuana, Mexico, with a focus on the role of public sex venues in relation to sexual risk behavior. Eligibility requirements were: biologically male, 18 years of age or older, resident of Tijuana, and self-reported anal or oral sex with a male partner in the past year. Participants completed an interviewer-administered, demographic and psychosocial survey, and were tested for HIV and syphilis. A hierarchical multiple linear regression model was tested to identify correlates of condomless anal sex. Thirty-eight percent of participants (N = 76) reported condomless anal sex with a male partner in the past 2 months. Higher levels of condomless anal sex were associated with higher levels of depressive symptoms, greater sexual compulsivity, and more frequent seeking out of sex partners in a public venue in the past 2 months. In view of these findings, we recommend the development of multi-level, “combination” interventions, which in the Mexican context should include enhanced condom promotion and distribution, improved availability and access to mental health treatment and counseling services, and expanded HIV/STI testing in public venues.

Correlates of Sexual Violence Among Men Who Have Sex With Men in Tijuana, Mexico

Sexual violence among men who have sex with men (MSM) is prevalent in developing countries and is associated with increased HIV/STI risk. Despite high HIV prevalence (20 %) among MSM in Tijuana, Mexico, little attention has been paid to the occurrence of sexual violence in this high-risk group. The present study used a syndemic conditions framework to examine correlates of sexual violence victimization in a sample of 201 MSM surveyed in Tijuana, Mexico during 2012 and 2013. Participants were recruited through respondent-driven sampling and underwent a 2-h baseline interview and testing for HIV and syphilis. Sexual violence was defined as any incident during the past year in which the participant had been raped, sexually molested, or sexually harassed. The majority of participants self-identified as gay or bisexual, had never married, were employed, and had a high school education or greater. The average age was 29.7 years. Thirty-nine percent reported sexual violence in the past year. A hierarchical multiple linear regression model predicting more experiences of sexual violence was tested. In a final model, a higher number of experiences of sexual violence was associated with a history of childhood sexual abuse, more adult experiences of homophobia, more depression and hostility symptoms, and not living with a spouse or steady partner. The findings from this study support a model of co-occurring psychosocial factors that increase the likelihood of sexual violence experiences among MSM. Multi-level approaches to the prevention of childhood and adult experiences of sexual violence and homophobia are needed to avert the development of adverse mental and physical health outcomes associated with sexual violence victimization.

HIV testing practices and the potential role of HIV self-testing among men who have sex with men in Mexico

The objective of this study was to characterize HIV testing practices among men who have sex with men in Mexico and intention to use HIV self-testing. In 2012, members of one of the largest social/sexual networking websites for men who have sex with men in Latin America completed an anonymous online survey. This analysis was restricted to HIV-uninfected men who have sex with men residing in Mexico. Multivariable logistic regression models were fit to assess factors associated with HIV testing and intention to use a HIV self-test. Of 4537 respondents, 70.9% reported ever having a HIV test, of whom 75.5% reported testing at least yearly. The majority (94.3%) indicated that they would use a HIV home self-test if it were available. Participants identifying as bisexual less often reported ever HIV testing compared to those identifying as gay/homosexual (adjusted odds ratio = 0.52, 95% confidence interval: 0.44-0.62). Having a physical exam in the past year was associated with increased ever HIV testing (adjusted odds ratio = 4.35, 95% confidence interval: 3.73-5.07), but associated with decreased interest in HIV self-testing (adjusted odds ratio = 0.66, 95% confidence interval: 0.48-0.89). The high intention to use HIV home self-testing supports the use of this method as an acceptable alternative to clinic- or hospital-based HIV testing.

Intersecting epidemics of HIV, HCV, and syphilis among soon-to-be released prisoners in Kyrgyzstan: Implications for prevention and treatment

BACKGROUND

Central Asia is afflicted with increasing HIV incidence, low antiretroviral therapy (ART) coverage and increasing AIDS mortality, driven primarily by people who inject drugs (PWID). Reliable data about HIV, other infectious diseases, and substance use disorders in prisoners in this region is lacking and could provide important insights into how to improve HIV prevention and treatment efforts in the region.

METHODS

A randomly sampled, nationwide biobehavioural health survey was conducted in 8 prisons in Kyrgyzstan among all soon-to-be-released prisoners; women were oversampled. Consented participants underwent computer-assisted, standardized behavioural health assessment surveys and testing for HIV, HCV, HBV, and syphilis. Prevalence and means were computed, and generalized linear modelling was conducted, with all analyses using weights to account for disproportionate sampling by strata.

RESULTS

Among 381 prisoners who underwent consent procedures, 368 (96.6%) were enrolled in the study. Women were significantly older than men (40.6 vs. 36.5; p=0.004). Weighted prevalence (%), with confidence interval (CI), for each infection was high: HCV (49.7%; CI: 44.8-54.6%), syphilis (19.2%; CI: 15.1-23.5%), HIV (10.3%; CI: 6.9-13.8%), and HBV (6.2%; CI: 3.6-8.9%). Among the 31 people with HIV, 46.5% were aware of being HIV-infected. Men, compared to women, were significantly more likely to have injected drugs (38.3% vs.16.0%; p=0.001). Pre-incarceration and within-prison drug injection, primarily of opioids, was 35.4% and 30.8%, respectively. Independent correlates of HIV infection included lifetime drug injection (adjusted odds ratio [AOR]=38.75; p=0.001), mean number of years injecting (AOR=0.93; p=0.018), mean number of days experiencing drug problems (AOR=1.09; p=0.025), increasing duration of imprisonment (AOR=1.08; p=0.02 for each year) and having syphilis (AOR=3.51; p=0.003), while being female (AOR=3.06; p=0.004) and being a recidivist offender (AOR=2.67; p=0.008) were independently correlated with syphilis infection.

CONCLUSION

Drug injection, syphilis co-infection, and exposure to increased risk during incarceration are likely to be important contributors to HIV transmission among prisoners in Kyrgyzstan. Compared to the community, HIV is concentrated 34-fold higher in prisoners. A high proportion of undiagnosed syphilis and HIV infections presents a significant gap in the HIV care continuum. Findings highlight the critical importance of evidence-based responses within prison, including enhanced testing for HIV and sexually transmitted infections, to stem the evolving HIV epidemic in the region.

Overlapping substance using high-risk groups and infectious diseases: how dynamic modelling can evaluate risk and target HIV prevention

It’s difficult to develop infectious disease interventions (such as for HIV) for overlapping high-risk populations such as people who inject drugs, men who have sex with men, and female sex workers, where there are multiple transmission routes. Recent advances in dynamic modelling of coinfection epidemics could disentangle the contributions of different risk groups and behaviours to help develop more efficient and effective prevention interventions.

Engagement in the HIV Care Continuum among Key Populations in Tijuana, Mexico

In Tijuana, Mexico, HIV is concentrated in sub-epidemics of key populations: persons who inject drugs (PWID), sex workers (SW), and men who have sex with men (MSM). To date, data on engagement in the HIV care continuum among these key populations, particularly in resource-constrained settings, are sparse. We pooled available epidemiological data from six studies (N = 3368) to examine HIV testing and treatment uptake in these key populations; finding an overall HIV prevalence of 5.7 %. Of the 191 identified HIV-positive persons, only 11.5 % knew their HIV-positive status and 3.7 % were on ART. Observed differences between these HIV-positive key populations suggest PWID (vs. non-PWID) were least likely to have previously tested or initiate HIV care. MSM (vs. non-MSM) were more likely to have previously tested but not more likely to know their HIV-positive status. Of persons aware of their HIV-positive status, SW (vs. non-SW) were more likely to initiate HIV care. Findings suggest engagement of key populations in HIV treatment is far below estimates observed for similarly resource-constrained generalized epidemics in sub-Saharan Africa. These data provide one of the first empirical-snapshots highlighting the extent of HIV treatment disparities in key populations.

HIV testing among men who have sex with men in Tijuana, Mexico: a cross-sectional study

OBJECTIVES

HIV testing is critical to the delivery of comprehensive HIV prevention and care services, yet coverage of sexual minorities by HIV testing programmes remains insufficient in many low- and middle-income countries, including Mexico. The objective of this study was to identify the prevalence and correlates of HIV testing among men who have sex with men (MSM) in Tijuana, Mexico.

METHODS

We conducted a cross-sectional study (2012-2013) among 189 MSM recruited via respondent-driven sampling (RDS). RDS-weighted logistic regression was used to identify correlates of prior HIV testing.

RESULTS

RDS-adjusted prevalence of prior and recent (≤ 12 months) HIV testing was 63.5% (95% CI 51.9% to 73.5%) and 36.8% (95% CI 25.4% to 46.4%), respectively. Prior HIV testing was positively associated with older age (adjusted OR (AOR)=1.09, 95% CI 1.04 to 1.15), being born in Tijuana (AOR=2.68, 95% CI 1.05 to 6.86), higher levels of education (AOR=2.65, 95% CI 1.08 to 6.53), identifying as homosexual or gay (AOR=3.73, 95% CI 1.48 to 9.42), being more 'out' about having sex with men (AOR=1.28, 95% CI:1.02 to 1.62), and a history of sexual abuse (AOR=3.24, 95% CI 1.06 to 9.86). Prior HIV testing was negatively associated with reporting more condomless anal intercourse acts (past 2 months) (AOR=0.95, 95% CI 0.92 to 0.98) and greater internalised homophobia (AOR=0.92, 95% CI 0.86 to 0.99).

CONCLUSIONS

Our findings indicate an urgent need for expanded HIV testing services for MSM in Tijuana. Innovative, non-stigmatising, confidential HIV testing interventions targeted at young, less educated, migrant and non-gay identifying MSM may facilitate HIV testing and timely linkage to HIV care and treatment within this population.

"Outness" as a Moderator of the Association Between Syndemic Conditions and HIV Risk-Taking Behavior Among Men Who Have Sex with Men in Tijuana, Mexico

Multiple psychosocial conditions tend to co-occur and contribute to higher risk for HIV among men who have sex with men (MSM), a phenomenon known as syndemics. Less is known about moderating factors that may attenuate the relation between syndemic conditions and sexual risk-taking. We examined disclosure of same-sex sexual behavior or "outness" as a moderating factor of the syndemic effect. We recruited a sample of MSM (n = 191) using respondent-driven sampling in Tijuana, Mexico. Participants completed a survey of syndemic conditions (i.e., substance use, depression, violence, internalized homophobia, and sexual compulsivity), sexual risk-taking (i.e., condom unprotected anal sex with a stranger in the past 2 months), and the degree to which they are "out" about sex with men. Consistent with previous research, we found that men who report more syndemic conditions show a greater prevalence of sexual risk-taking. As predicted, men who were out to more people showed a weaker association between syndemic conditions and sexual risk-taking, whereas men who were out to fewer people showed the strongest association. This study is the first to provide evidence of "outness" as a moderating factor that attenuates syndemic effects on sexual risk-taking. Building upon previous research, the data suggest that "outness" may be a resilience factor for MSM in Tijuana. HIV prevention intervention implications are discussed.

Amphetamine-type stimulant use among men who have sex with men (MSM) in Vietnam: Results from a socio-ecological, community-based study

INTRODUCTION

Amphetamine-type-stimulants (ATS) use is associated with HIV-related sexual risk behaviours and is an emergent problem among men who have sex with men (MSM) in Vietnam. The purpose of this study is to describe ATS use patterns and understand the correlates of recent methamphetamine use from a socio-ecological perspective.

METHODS

From September through December, 2014, 622 MSM were recruited in Hanoi and Ho Chi Minh City, Vietnam. We collected information on demographic characteristics, HIV testing behaviours, use of ATS and other recreational drugs (ever and recently), sexual sensation seeking, depressive mood, experienced and internalized stigma related to homosexuality, social involvement with other MSM, and perceptions of ATS use in MSM networks. We performed descriptive statistics to describe ATS use patterns and multivariate logistic regression to establish independent correlates of recent methamphetamine use.

RESULTS

Nearly one-third (30.4%) had ever used ATS, including 23.6% who had used methamphetamine, 4.3% who had used amphetamine ('speed') and 20.9% who had used ecstasy. 20.1% and 11.9% had ever used methamphetamine and ecstasy, respectively, during sex. Eighteen percent of methamphetamine users were classified as engaged in high-risk use. Recent methamphetamine use (in the last 3 months) was associated with participants perceiving more methamphetamine use in their MSM network, recent sex work, and higher sexual sensation seeking scores.

CONCLUSIONS

ATS use is relatively prevalent among MSM sampled in Vietnam's main cities. Interventions to address methamphetamine are warranted for MSM in Vietnam. Methamphetamine treatments are needed for high-risk users.

HIV Transmission Networks in the San Diego-Tijuana Border Region

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.

FINDINGS

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.

INTERPRETATION

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.

FUNDING

NIH, VA, and Pendleton Foundation.