Sex Work Venue Disorder and HIV/STI Risk Among Female Sex Workers in Two México-US Border Cities: A Latent Class Analysis.

Research increasingly recognizes the importance of social and built environments in shaping health, including risks for and outcomes related to HIV and sexually transmitted infections (STI), but research on sex work venues is limited. We use latent class analysis to identify patterns of sex work venue characteristics and factors associated with class membership in two México-US border cities. Among 603 female sex workers (FSW), three classes of sex work venues were identified: low, medium, and high disorder venues, characterized by level of violence, policing and drug activity. In multivariable analysis, risk exposures and outcomes varied by class, suggesting the need for place-based interventions that are tailored to specific venue profiles and that promote FSW health and safety in the workplace.

Migration and Mobility: Correlates of Recent HIV Testing Among Substance Using Female Sex Workers at the Mexico-Guatemala Border.

The goal of this paper is to determine the association between traveling to engage in sex work in another country and recent access to HIV testing among substance-using female sex workers (FSWs) in the Mexico-Guatemala border region. From 2012 to 2015, through modified time-location sampling and peer referral, 255 FSWs were recruited at Mexico's southern border. Participants completed questionnaires on sociodemographics, migration and mobility experiences, work environment factors, and substance use. A conceptual framework, as depicted by a directed acyclic graph (DAG), guided our analysis. Crude and adjusted logistic regression models were used to evaluate the relationships between mobility experiences and HIV testing in the past year. Overall HIV testing was low (41%); after considering relevant covariates (i.e., interaction with health services and organizations, and sex work characteristics) traveling to engage in sex work in another country was found to be positively associated with HIV testing in the past year. Future efforts need to consider voluntary and non-stigmatizing prevention HIV services and focus on reaching out to less mobile women.

RESUMEN: El objetivo de este artículo es determinar la asociación entre viajar a otro país para ejercer el comercio sexual y el acceso a una prueba reciente de VIH, en una población de mujeres trabajadoras sexuales en la frontera de México con Guatemala. Entre el 2012 y 2015, utilizando un muestreo por conveniencia y por referencia de pares, se invitó a 255 mujeres trabajadoras sexuales en la frontera sur de México a participar en este proyecto de investigación. Las participantes completaron una encuesta que comprendió preguntas sociodemográficas así como experiencias de migración y movilidad, características del trabajo sexual, y patrones de uso de sustancia. Utilizamos un marco conceptual que se ilustra en una Gráfica Acíclica Dirigida (DAG) el cual sirvió para guiar nuestro análisis. Realizamos análisis de regresión logística cruda y ajustada para evaluar la asociación entre experiencias de movilidad y haber recibido una prueba de VIH en el último año. En general, el porcentaje de haber recibido una prueba de VIH en el último año fue bajo (41%); después de considerar covariables relevantes; (ej., interacción con organizaciones y servicios de salud, características del trabajo sexual) encontramos que viajar a otro país para ejercer el comercio sexual está asociado con haber recibido una prueba de VIH en el último año. Es importante que, en el futuro, se concentren esfuerzos en servicios de prevención del VIH que sean voluntarios, no estigmatizantes, y que se enfoquen en mujeres trabajadoras sexuales menos móviles.

Economic vulnerability, violence, and sexual risk factors for HIV among female sex workers in Tijuana, Mexico.

Economic vulnerability is often reported to underlie involvement in sex work among female sex workers (FSW), but may also create urgency in women's work, limiting women's negotiating power with clients and in turn, increasing their vulnerability for violence and HIV. This study assessed economic vulnerability in relation to violence and sexual risk behaviors for HIV among a sample of FSW in Tijuana, Mexico. FSW at least 18 years of age were recruited through venue-based sampling for a survey (n = 228) and in-depth interviews (n = 50) to investigate HIV risk factors in this region. Using crude and adjusted logistic regression models, we assessed lack of financial support from others as well as reports of financial hardship separately in relation to experiencing sexual violence (e.g. by clients, police, relationship partners, in the past 6 months), physical violence (past 6 months), STI diagnosis, and inconsistent condom use (past 30 days). Qualitative interviews (n = 50), conducted with a subsample of the survey participants, were also examined for related themes. FSW who reported no financial support were more likely to report sexual violence (OR = 2.1; 95% CI:1.1-4.2). FSW who reported financial hardship were more likely to experience sexual violence (OR = 1.9; 95% CI:1.1-3.6) and physical violence (OR = 1.9; 95% CI:1.1-3.6), as well as to report past 30-day inconsistent condom use (OR = 2.4; 95%CI: 1.3-4.6) and to test positive for an STI (OR = 1.9; 95% CI:1.1-3.4). Qualitative data substantiated these findings. Findings suggest that interventions to improve economic well-being may be useful to prevent the intersecting concerns of violence and HIV among FSW.

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.

RESUMEN: Tijuana, México, tiene una epidemia de VIH concentrada en poblaciones claves (PC) superpuestas que incluyen personas que se inyectan drogas (PID), trabajadoras sexuales (MTS), sus clientes hombres, y hombres que tienen sexo con hombres (HSH). Desarrollamos un modelo dinámico de transmisión de VIH en estas PC para determinar hasta dónde sus necesidades no atendidas de prevención y tratamiento dirigen la transmisión del VIH. Para 2020­2029 estimamos la proporción de nuevas infecciones adquiridas en cada PC, y la proporción atribuida a sus comportamientos de riesgo sin protección. Estimamos que 43.7% y 55.3% de nuevas infecciones se dan en HSH y PID, respectivamente, con MTS y clientes conformando < 10% de nuevas infecciones. Las proyecciones sugieren que 93.8% de nuevas infecciones en 2020­2029 se deberán a sexo sin protección en HSH o uso inseguro de drogas inyectables. Dar prioridad a intervenciones que atienden los riesgos sexual y de inyección en HSH y PID es crítico para controlar el VIH en Tijuana.

The influence of migration in substance use practices and HIV/STI-related risks of female sex workers at a dynamic border crossing.

We explored the association of international migration with substance use and HIV/STI risk factors among female sex workers (FSW). Using modified time-location sampling, we recruited 266 FSW at the Mexico-Guatemala border. Crude and adjusted logistic regression models were used to evaluate the relationships. HIV risks, such as frequent hard drug use and drug use in another country, were greater for migrant compared to nonmigrant FSW. However, more migrant versus nonmigrant FSW reported consistent condom use with clients and having a health card. Our study highlights regional patterns of substance use among FSW and risk or protective behaviors related to migration status.

Struggling bodies at the border: migration, violence and HIV vulnerability in the Mexico/Guatemala border region.

The Mexico-Guatemala border is the site of significant movement of people whose principal destination is the USA. The first step, to cross Mexico, is considered as one of the most dangerous routes in the world for undocumented migrants. For some male migrants and displaced persons from Honduras, El Salvador and Guatemala, initiating sex work in the Mexican border city of Tapachula has become a way to earn money to survive during the trip northward - providing funds to keep traveling and decrease the danger of being killed or kidnaped by organized crime groups. Non-injected drug use during sex work with men and/or women is a common praxis for this purpose, and is linked to HIV risk activities such as unprotected sex. Our study is based on ethnographic fieldwork with observation and interviews and within a relational approach understanding the processes subject/structure, sociopolitical/cultural and global/local, not as oppositions, rather as linkages visible through actors' points of view and praxis. The productions of politics and cultures related to structural vulnerability to HIV infection are embedded in local and global borderization processes where legal and illegal transnational forces, states' frameworks and social groups play a linked role. The economies of structural, symbolic and direct violence affect migratory patterns, institutional interactions and social and cultural relations with the local population. In this context, social representations and praxis about unprotected sex and drug use are the locus of struggling bodies at the border.

Associations between household environmental factors and immature mosquito abundance in Quetzaltenango, Guatemala.

BACKGROUND: Aedes aegypti-borne diseases are becoming major public health problems in tropical and sub-tropical regions. While socioeconomic status has been associated with larval mosquito abundance, the drivers or possible factors mediating this association, such as environmental factors, are yet to be identified. We examined possible associations between proximity to houses and roads and immature mosquito abundance, and assessed whether these factors and mosquito prevention measures mediated any association between household environmental factors and immature mosquito abundance. METHODS: We conducted two cross-sectional household container surveys in February-March and November-December, 2017, in urban and rural areas of Quetzaltenango, Guatemala. We used principal components analysis to identify factors from 12 variables to represent the household environment. One factor which included number of rooms in house, electricity, running water, garbage service, cable, television, telephone, latrine, well, and sewer system, was termed "environmental capital." Environmental capital scores ranged from 0 to 5.5. Risk factors analyzed included environmental capital, and distance from nearest house/structure, paved road, and highway. We used Poisson regression to determine associations between distance to nearest house/structure, roads, and highways, and measures of immature mosquito abundance (total larvae, total pupae, and positive containers). Using cubic spline generalized additive models, we assessed non-linear associations between environmental capital and immature mosquito abundance. We then examined whether fumigation, cleaning containers, and distance from the nearest house, road, and highway mediated the relationship between environmental capital and larvae and pupae abundance. RESULTS: We completed 508 household surveys in February-March, and we revisited 469 households in November-December. Proximity to paved roads and other houses/structures was positively associated with larvae and pupae abundance and mediated the associations between environmental capital and total numbers of larvae/pupae (p ≤ 0.01). Distance to highways was not associated with larval/pupal abundance (p ≥ 0.48). Households with the lowest and highest environmental capital had fewer larvae/pupae than households in the middle range (p < 0.01). CONCLUSIONS: We found evidence that proximity to other houses and paved roads was associated with greater abundance of larvae and pupae. Understanding risk factors such as these can allow for improved targeting of surveillance and vector control measures in areas considered at higher risk for arbovirus transmission.

Substance Use among Female Sex Workers in Two US-Mexico Border Cities: Associations with Age of Entry.

BACKGROUND: Research has documented consistent associations between entry into sex work as a minor and sexual HIV risk. However, previous studies have not examined whether substance use and related HIV risk are elevated among those who enter sex work under age 18. METHODS: Quantitative data were collected via time-location sampling of 603 female sex workers (FSWs) ages 18 years and older residing in two Mexico-US border cities. Age of entry into sex work (categorized as 15 years or younger, 16-17 years, or 18 years and older) was assessed as a predictor of substance use (forced and voluntary) within the first month post-entry and recent (past 30 days) substance use with clients. RESULTS: Compared to those who entered as adults, participants who entered sex work at age 15 or younger were significantly more likely to report drug use (AOR = 5.2, CI = 2.9-8.9) and forced drug use within the first 30 days of entry (AOR= 6.0, CI = 1.9-18.9), as well as past month drug use with clients (AOR= 3.4, CI = 1.9-5.8). Similar results were found among participants who entered sex work at age 16-17. CONCLUSIONS: Increased risk of recent substance use with clients indicates continuing elevated risk for those entering sex work at these early ages. Early and forced substance use at entry may underlie the elevated risk of HIV infection consistently observed among this population.

Childhood Experiences of Sexual Violence, Pregnancy, and Marriage Associated With Child Sex Trafficking Among Female Sex Workers in Two US-Mexico Border Cities.

OBJECTIVES: To quantitatively assess the relationships of childhood experiences of marriage, pregnancy, and sexual violence with underage sex trafficking. METHODS: Cross-sectional survey data from a population-based sample of 603 female sex workers from Tijuana and Ciudad Juárez, Mexico, were collected in 2013 and 2014, and we analyzed the data to evaluate relationships between pregnancy, marriage, and sexual violence when younger than 16 years, and child sex trafficking. RESULTS: Adjusted odds of child sex trafficking among those who experienced pregnancy, marriage, and childhood sexual violence when younger than 16 years in combined models were 2.8 (95% confidence interval [CI] = 1.8, 4.3), 1.7 (95% CI = 0.99, 2.8), and 1.7 (95% CI = 1.01, 3.0), respectively, relative to others (n = 603). For 89.8%, 78.0%, and 97.0% of those who had an experience of pregnancy (n = 69), marriage (n = 50), or sexual violence (n = 33) when younger than 16 years, respectively, the experience occurred before or the same year as sex trafficking. CONCLUSIONS: These results provide empirical evidence of modifiable risk factors for child sex trafficking that could be integrated into the prevention efforts and protocols of health clinics and governmental agencies in Mexico currently working to reduce underage pregnancy, marriage, and sexual violence.

Influence of indoor work environments on health, safety, and human rights among migrant sex workers at the Guatemala-Mexico Border: a call for occupational health and safety interventions.

BACKGROUND: Migrant women are over-represented in the sex industry, and migrant sex workers experience disproportionate health inequities, including those related to health access, HIV and sexually transmitted infections (STIs), and violence. Despite calls for occupational sex work interventions situated in labour rights frameworks, there remains a paucity of evidence pertaining to migrant sex workers' needs and realities, particularly within Mexico and Central America. This study investigated migrant sex workers' narratives regarding the ways in which structural features of work environments shape vulnerability and agency related to HIV/STI prevention and violence at the Guatemala-Mexico border. METHODS: Drawing on theoretical perspectives on risk environments and structural determinants of HIV in sex work, we analyzed in-depth interviews, focus groups, and ethnographic fieldwork conducted with 39 migrant sex workers in indoor work environments between 2012 and 2015 in Tecún Umán, Guatemala. RESULTS: Participant narratives revealed the following intersecting themes to be most closely linked to safety and agency to engage in HIV/STI prevention: physical features of indoor work environments (e.g., physical layout of venue, proximity to peers and third parties); social norms and practices for alcohol use within the workplace; the existence and nature of management practices and policies on health and safety practices; and economic influences relating to control over earnings and clients. Across work environments, health and safety were greatly shaped by human rights concerns stemming from workplace interactions with police, immigration authorities, and health authorities. CONCLUSIONS: Physical isolation, establishment norms promoting alcohol use, restricted economic agency, and human rights violations related to sex work policies and immigration enforcement were found to exacerbate risks. However, some establishment policies and practices promoted 'enabling environments' for health and safety, supporting HIV/STI prevention, economic agency, and protection from violence and exploitation; these practices and policies were especially crucial for recent migrants. Policy reforms and structural workplace interventions tailored to migrant sex workers' needs are recommended to promote improved working conditions and migrant sex workers' health, safety, and human rights.

Motherhood and Risk for Human Immunodeficiency Virus/Sexually Transmitted Infections Among Female Sex Workers in the Mexico-US Border Region.

BACKGROUND: Globally, female sex workers (FSWs) have been identified as a high-risk group for human immunodeficiency virus (HIV) and sexually transmitted infections (STIs). However, as women of reproductive age, FSWs also have children. Few studies have investigated if financial responsibilities associated with motherhood increase women's vulnerability to HIV and STIs among FSWs. METHODS: From March 2013 to March 2014, 603 FSWs aged ≥18 years were recruited from Tijuana and Ciudad Juarez (Mexico) to participate in a study assessing HIV/STI risk environments. RESULTS: Findings from logistic regression models indicate that FSWs who reported motherhood were more likely to report (in the past 30 days): a higher client volume (>30 clients) (adjusted odds ratio [AOR], 1.91; 95% confidence interval [CI], 1.27-2.87) and always using alcohol right before or during sex with clients in the past 30 days (AOR, 1.77; 95% CI, 1.19-2.61). In contrast, they were more likely to report consistent condom use for vaginal or anal sex with clients (AOR, 1.68; 95% CI, 1.10-2.55), less likely to report using drugs right before or during sex with clients (AOR, 0.38; 95% CI, 0.26-0.56) and less likely to have tested positive for STIs at baseline (AOR, 0.63; 95% CI, 0.43-0.91). CONCLUSIONS: These results provide a glimpse of the complex relationship between motherhood and women who are sex workers. Understanding the convergence of motherhood and sex work and how this can influence a woman's decision when engaging in sex work and affect her health is essential to designing effective programs addressing reduce risk for HIV and STIs among FSWs in this region and elsewhere.

High prevalence of very-low Plasmodium falciparum and Plasmodium vivax parasitaemia carriers in the Peruvian Amazon: insights into local and occupational mobility-related transmission.

BACKGROUND: The incidence of malaria due both to Plasmodium falciparum and Plasmodium vivax in the Peruvian Amazon has risen in the past 5 years. This study tested the hypothesis that the maintenance and emergence of malaria in hypoendemic regions such as Amazonia is determined by submicroscopic and asymptomatic Plasmodium parasitaemia carriers. The present study aimed to precisely quantify the rate of very-low parasitaemia carriers in two sites of the Peruvian Amazon in relation to transmission patterns of P. vivax and P. falciparum in this area. METHODS: This study was carried out within the Amazonian-ICEMR longitudinal cohort. Blood samples were collected for light microscopy diagnosis and packed red blood cell (PRBC) samples were analysed by qPCR. Plasma samples were tested for total IgG reactivity against recombinant PvMSP-10 and PfMSP-10 antigens by ELISA. Occupation and age 10 years and greater were considered surrogates of occupation-related mobility. Risk factors for P. falciparum and P. vivax infections detected by PRBC-qPCR were assessed by multilevel logistic regression models. RESULTS: Among 450 subjects, the prevalence of P. vivax by PRBC-PCR (25.1%) was sixfold higher than that determined by microscopy (3.6%). The prevalence of P. falciparum infection was 4.9% by PRBC-PCR and 0.2% by microscopy. More than 40% of infections had parasitaemia under 5 parasites/µL. Multivariate analysis for infections detected by PRBC-PCR showed that participants with recent settlement in the study area (AOR 2.1; 95% CI 1.03:4.2), age ≥ 30 years (AOR 3.3; 95% CI 1.6:6.9) and seropositivity to P. vivax (AOR 1.8; 95% CI 1.0:3.2) had significantly higher likelihood of P. vivax infection, while the odds of P. falciparum infection was higher for participants between 10 and 29 years (AOR 10.7; 95% CI 1.3:91.1) and with a previous P. falciparum infection (AOR 10.4; 95% CI 1.5:71.1). CONCLUSIONS: This study confirms the contrasting transmission patterns of P. vivax and P. falciparum in the Peruvian Amazon, with stable local transmission for P. vivax and the source of P. falciparum to the study villages dominated by very low parasitaemia carriers, age 10 years and older, who had travelled away from home for work and brought P. falciparum infection with them.

HIV Risk Behaviors and Correlates of Inconsistent Condom Use Among Substance Using Migrants at the Mexico/Guatemala Border.

This study assessed correlates of inconsistent condom use with casual partners and the prevalence of sexual risk behaviors and STIs in the Mexico/Guatemala border region using a sample of 392 migrants (303 men, 85 women) who reported current substance use or problem drinking. We ran separate univariate logistic regression models for men and women, and multivariate logistic regression models for men only. Prevalence of syphilis was 1.2% among women and 2.3% among men; HIV prevalence was 2.4% among women and 1.3% among men. Inconsistent condom use with casual partners was higher in women with greater education and lower among women who sold sex. In men, less access to free condoms, drug use with sexual partners, and drug use before sex were independently associated with inconsistent condom use with casual partners. Sexual and substance use risk behaviors were common, and HIV/STI prevention efforts should target both genders and expand beyond most-at risk populations.

Structural Determinants of Client Perpetrated Violence Among Female Sex Workers in Two Mexico-U.S. Border Cities.

Female sex workers (FSWs) are disproportionately affected by both HIV and gender-based violence, such as that perpetrated by clients (CPV). We used a structural determinants framework to assess correlates of physical or sexual CPV in the past 6 months among FSWs in the Mexico/U.S. border cities of Ciudad Juárez and Tijuana. Bivariate and multivariate logistic regression analysis identified individual, client, interpersonal, work environment and macrostructural factors associated with recent CPV. Among 496 FSWs, 5 % experienced recent CPV. Witnessing violence towards other FSWs in one's neighborhood (aOR 5.6, 95 % CI 1.8-17.2), having a majority of foreign (aOR 3.5, 95 % CI 1.4-8.4) or substance using (aOR 4.0, 95 % CI 1.5-10.4) clients, and being a street worker (aOR 3.0, 95 % CI 1.1-7.7) were independently associated with recent CPV. Our findings underscore the vulnerability of FSWs and the need to design policies and interventions addressing macro-level influences on CPV rather than exclusively targeting individual behaviors.

Utilization of Google enterprise tools to georeference survey data among hard-to-reach groups: strategic application in international settings.

BACKGROUND: As geospatial data have become increasingly integral to health and human rights research, their collection using formal address designations or paper maps has been complicated by numerous factors, including poor cartographic literacy, nomenclature imprecision, and human error. As part of a longitudinal study of people who inject drugs in Tijuana, Mexico, respondents were prompted to georeference specific experiences. RESULTS: At baseline, only about one third of the 737 participants were native to Tijuana, underscoring prevalence of migration/deportation experience. Areas frequented typically represented locations with no street address (e.g. informal encampments). Through web-based cartographic technology and participatory mapping, this study was able to overcome the use of vernacular names and difficulties mapping liminal spaces in generating georeferenced data points that were subsequently analyzed in other research. CONCLUSION: Integrating low-threshold virtual navigation as part of data collection can enhance investigations of mobile populations, informal settlements, and other locations in research into structural production of health at low- or no cost. However, further research into user experience is warranted.

Migration, violence, and safety among migrant sex workers: a qualitative study in two Guatemalan communities.

Despite reports of high levels of violence among women migrants in Central America, limited evidence exists regarding the health and safety of migrant sex workers in Central America. This study is based on 16 months of field research (November 2012-February 2014), including ethnographic fieldwork, in-depth interviews, and focus groups conducted with 52 internal and international migrant female sex workers in Tecún Umán and Quetzaltenango, Guatemala, key transit and destination communities for both international and internal migrants. The analysis explored migration-related determinants of susceptibility to violence experienced by migrant sex workers across different phases of migration. Violence in home communities and economic considerations were key drivers of migration. Unsafe transit experiences (eg undocumented border crossings) and negative interactions with authorities in destination settings (eg extortion) contributed to migrant sex workers' susceptibility to violence, while enhanced access to information on immigration policies and greater migration and sex work experience were found to enhance agency and resilience. Findings suggest the urgent need for actions that promote migrant sex workers' safety in communities of origin, transit, and destination, and programmes aimed at preventing and addressing human rights violations within the context of migration and sex work.

Emerging and reemerging neglected tropical diseases: a review of key characteristics, risk factors, and the policy and innovation environment.

In global health, critical challenges have arisen from infectious diseases, including the emergence and reemergence of old and new infectious diseases. Emergence and reemergence are accelerated by rapid human development, including numerous changes in demographics, populations, and the environment. This has also led to zoonoses in the changing human-animal ecosystem, which are impacted by a growing globalized society where pathogens do not recognize geopolitical borders. Within this context, neglected tropical infectious diseases have historically lacked adequate attention in international public health efforts, leading to insufficient prevention and treatment options. This subset of 17 infectious tropical diseases disproportionately impacts the world's poorest, represents a significant and underappreciated global disease burden, and is a major barrier to development efforts to alleviate poverty and improve human health. Neglected tropical diseases that are also categorized as emerging or reemerging infectious diseases are an even more serious threat and have not been adequately examined or discussed in terms of their unique risk characteristics. This review sets out to identify emerging and reemerging neglected tropical diseases and explore the policy and innovation environment that could hamper or enable control efforts. Through this examination, we hope to raise awareness and guide potential approaches to addressing this global health concern.

Polydrug Use and HIV Risk Among People Who Inject Heroin in Tijuana, Mexico: A Latent Class Analysis.

BACKGROUND: Although most people who inject drugs (PWID) in Tijuana, Mexico, primarily inject heroin, injection and non-injection use of methamphetamine and cocaine is common. We examined patterns of polydrug use among heroin injectors to inform prevention and treatment of drug use and its health and social consequences. METHODS: Participants were PWID residing in Tijuana, aged ≥18 years who reported heroin injection in the past six months and were recruited through respondent-driven sampling (n = 1,025). Latent class analysis was conducted to assign individuals to classes on a probabilistic basis, using four indicators of past six-month polydrug and polyroute use: cocaine injecting, cocaine smoking or snorting, methamphetamine injecting, and methamphetamine smoking or snorting. Latent class membership was regressed onto covariates in a multinomial logistic regression. RESULTS: Latent class analyses testing 1, 2, 3, and 4 classes were fit, with the 3-class solution fitting best. Class 1 was defined by predominantly heroin use (50.2%, n = 515); class 2 by methamphetamine and heroin use (43.7%, n = 448), and class 3 by methamphetamine, cocaine, and heroin use (6.0%, n = 62). Bivariate and multivariate analyses indicated a group of methamphetamine and cocaine users that exhibited higher-risk sexual practices and lower heroin injecting frequency, and a group of methamphetamine users who were younger and more likely to be female. CONCLUSIONS: Discrete subtypes of heroin PWID were identified based on methamphetamine and cocaine use patterns. These findings have identified subtypes of heroin injectors who require more tailored interventions to reduce the health and social harms of injecting drug use.

Evaluating outcome-correlated recruitment and geographic recruitment bias in a respondent-driven sample of people who inject drugs in Tijuana, Mexico.

Respondent-driven sampling's (RDS) widespread use and reliance on untested assumptions suggests a need for new exploratory/diagnostic tests. We assessed geographic recruitment bias and outcome-correlated recruitment among 1,048 RDS-recruited people who inject drugs (Tijuana, Mexico). Surveys gathered demographics, drug/sex behaviors, activity locations, and recruiter-recruit pairs. Simulations assessed geographic and network clustering of active syphilis (RPR titers ≥1:8). Gender-specific predicted probabilities were estimated using logistic regression with GEE and robust standard errors. Active syphilis prevalence was 7 % (crude: men = 5.7 % and women = 16.6 %; RDS-adjusted: men = 6.7 % and women = 7.6 %). Syphilis clustered in the Zona Norte, a neighborhood known for drug and sex markets. Network simulations revealed geographic recruitment bias and non-random recruitment by syphilis status. Gender-specific prevalence estimates accounting for clustering were highest among those living/working/injecting/buying drugs in the Zona Norte and directly/indirectly connected to syphilis cases (men: 15.9 %, women: 25.6 %) and lowest among those with neither exposure (men: 3.0 %, women: 6.1 %). Future RDS analyses should assess/account for network and spatial dependencies.

Substance use, economic vulnerability, and HIV/STI risk among female sex workers in Mexico.

BACKGROUND: Economic hardship (e.g., difficulty to pay for basic needs) has been associated with increased HIV/STI risk among female sex workers (FSW), and may be exacerbated by high levels of substance use. Few studies have assessed the intersection of economic hardship, substance use, and HIV/STI risk among FSW. METHODS: Quantitative data were collected via questionnaires among 469 FSW residing in Tijuana and Ciudad Juarez, Mexico. Using logistic regression, we assessed the role of economic hardship on the association between substance use (past 30-days alcohol use, drug use, or injection drugs use with clients, and past 6-months drug use) and testing positive for an STI (also an indicator of HIV risk). RESULTS: Drug use in the preceding six months was significantly associated with testing positive for an STI (AOR = 1.8, CI: 1.1 = 2.9, p = .02); no difference in this association was found by whether women reported economic hardship. Past 30-day drug use with clients was associated with STI infection, but only among those who did not report economic hardship (AOR = 1.5, 95% CI: 1.1-1.9, p < .01). CONCLUSIONS: Findings suggest that economic hardship influences the association between substance use and increased risk for HIV/STI among FSW; however, these associations may be more complex than previously hypothesized.