Correlates of perceived risk of HIV infection among persons who inject drugs in Tijuana, Baja California, Mexico / Correlaciones de percepción de riesgo de infección con VIH entre personas que se inyectan droga en Tijuana, Baja California, México

Objective. We identified correlates of perceived risk of HIV infection among persons who inject drugs (PWID) in Tijuana. Materials and methods. PWID ≥18 years of age who injected drugs in the past month were recruited between 2006-2007 and completed risk assessment interviews and serologic testing for HIV, syphilis, and tuberculosis. Logistic regression was used to determine factors associated with high-perceived risk of HIV infection. Results. Among 974 PWID, HIV prevalence was 4.4%; 45.0% of participants perceived themselves to be more likely to become HIV infected relative to other PWID in Tijuana. Participants who reported high-perceived risk of HIV infection participated in high-risk behaviors such as injecting with used syringes, transactional sex, and were less likely to have had an HIV test. Conclusions. Recognition of HIV infection risk was associated with high risk behaviors and markers of vulnerability. Findings support efforts to encourage HIV testing and access to health care for this vulnerable population.

Objetivo. Identificar factores correlacionados con el riesgo percibido de contraer VIH entre personas que se inyectan drogas (PID) en Tijuana. Material y métodos. Entre 2006-2007 se reclutaron PID ≥18 años de edad que se inyectaron drogas en el último año previo al estudio y completaron entrevistas para evaluación de riesgos y pruebas serológicas para VIH, sífilis y tuberculosis. Se utilizó regresión logística para determinar factores asociados con alto-riesgo percibido para la infección del VIH. Resultados. En los 974 PID la prevalencia de VIH fue 4.4%; 45.0% se consideró con mayor probabilidad de infectarse con VIH en relación con otros PID en Tijuana. Los participantes que reportaron alto riesgo percibido participaron en comportamientos de alto riesgo como inyectarse con jeringas usadas y transacción sexual, y tenían menos probabilidades de haber tenido una prueba de VIH. Conclusiones. Reconocer el riesgo del VIH se asoció con comportamientos de alto riesgo y marcadores de vulnerabilidad. Los resultados apoyan los esfuerzos para fomentar las pruebas para VIH y acceso a servicios de salud para esta población vulnerable.

Tuberculosis testing among populations with high HIV risk in Tijuana, Baja California, Mexico / Prueba de tuberculosis en poblaciones con riesgo alto de VIH en Tijuana, Baja California, México

OBJECTIVE: To assess the prevalence of prior tuberculin skin testing (TST) among populations at risk for HIV infection in Tijuana, Mexico, and to identify factors associated with TST. METHODS: Sex workers, injection drug users, noninjecting drug users, and homeless persons > 18 years old were recruited by using targeted sampling for risk assessment interviews and serologic testing for HIV and Mycobacterium tuberculosis infection. Univariate and multivariate logistic regression were used to identify correlates of self-reported TST history. RESULTS: Of 502 participants, 38.0% reported prior TST, which was associated with previous incarceration in the United States of America [odds ratio (OR) = 13.38; 95% confidence interval (CI) = 7.37-24.33] and injection drug use (OR = 1.99; 95% CI = 1.27- 3.11). Positive results on serologic tests for M. tuberculosis infection (57%) and HIV (4.2%) were not associated with a prior TST. CONCLUSIONS: A history of TST was lower in HIV-positive participants even though TST is indicated for persons with HIV in Mexico. Fewer than half the individuals at high risk for HIV in this study had a history of TST; however, TST was fairly common among those individuals with a prior history of incarceration. Increased tuberculosis screening is needed for populations at risk of contracting HIV in Tijuana, particularly those outside of criminal justice settings.

OBJETIVO: Evaluar la prevalencia de la prueba de la tuberculina previa, e identificar los factores asociados con ella, en poblaciones con riesgo de infección por el VIH en Tijuana, México. MÉTODOS: Se reclutó a profesionales del sexo, consumidores de drogas inyectables y no inyectables y personas sin hogar > 18 años de edad mediante un muestreo dirigido a fin de efectuar entrevistas para evaluar el riesgo y pruebas serológicas para la infección por el VIH y Mycobacterium tuberculosis. Para identificar la correlación de los antecedentes de la prueba de la tuberculina proporcionados por el propio individuo se usó regresión logística de una sola variable y con múltiples variables. RESULTADOS: De 502 participantes, 38,0% informaron una prueba de la tuberculina previa, que se asoció con encarcelamiento anterior en los Estados Unidos de América (razón de posibilidades [OR] = 13,38; intervalo de confianza de 95% [IC] = 7,37-24,33) y consumo de drogas inyectables (OR = 1,99; IC de 95% = 1,27-3,11). Los resultados positivos en las pruebas serológicas para la infección con M. tuberculosis (57%) y VIH (4,2%) no se asociaron con una prueba de la tuberculina previa. CONCLUSIONES: Los antecedentes de una prueba de la tuberculina fueron menores en los participantes seropositivos para el VIH, a pesar de que en México esta prueba está indicada en las personas con VIH. En este estudio menos de la mitad de los individuos con alto riesgo de VIH tenían antecedentes de la prueba de la tuberculina; sin embargo, esta fue bastante frecuente en los individuos con antecedentes de encarcelamiento. En las poblaciones en riesgo de contraer el VIH en Tijuana se requiere un mayor tamizaje de tuberculosis, en particular en aquellas no relacionadas con el ambiente de la justicia penal.

Mexico’s northern border conflict: collateral damage to health and human rights of vulnerable groups / El conflicto en la frontera norte de México: daños colaterales a la salud y los derechos humanos en grupos vulnerables

Objective. To compare distributions of human rights violations and disease risk; to juxtaposethese patterns against demographic and structural environmental variables, and to formulateimplications for structural interventions.Methods. Female sex workers who inject drugs were surveyed in Tijuana and CiudadJuarez, Mexico. Structured interviews and testing for sexually transmitted infections (STIs)were conducted (October 2008 to October 2009). Frequencies of individual and environmentalfactors, including police abuse, risk of HIV infection, and protective behaviors, were comparedbetween sites using univariate logistic regression.Results. Of 624 women, almost half reported police syringe confiscation despite syringesbeing legal; 55.6% reported extortion (past 6 months), with significantly higher proportions inCiudad Juarez (P < 0.001). Reports of recent solicitation of sexual favors (28.5% in Tijuana,36.5% in Ciudad Juarez, P = 0.04) and sexual abuse (15.7% in Tijuana, 18.3% in CiudadJuarez) by police were commonplace. Prevalence of STIs was significantly lower in Tijuanathan in Ciudad Juarez (64.2% and 83.4%, P < 0.001), paralleling the lower prevalence ofsexual risk behaviors there. Ciudad Juarez respondents reported significantly higher mediannumber of monthly clients (6.8 versus 1.5, P < 0.001) and lower median pay per sex act(US$ 10 versus US$ 20, P < 0.001) (in the past month). Relative to Tijuana, security deployment,especially the army’s presence, was perceived to have increased more in Ciudad Juarezin the past year (72.1% versus 59.2%, P = 0.001).Conclusions. Collateral damage from police practices in the context of Mexico’s drug conflictmay affect public health in the Northern Border Region. Itinerant officers may facilitate diseasespread beyond the region. The urgency for mounting structural interventions is discussed.

Objetivo. Comparar las distribuciones de las violaciones a los derechos humanos yel riesgo de enfermedades; yuxtaponer los patrones obtenidos con las variables demográficasy estructurales del entorno, y formular las implicaciones de llevar a cabointervenciones estructurales.Métodos. Se entrevistaron trabajadoras del sexo que consumían drogas inyectablesen Tijuana y Ciudad Juárez, México. Entre octubre del 2008 y octubre del 2009 sellevaron a cabo entrevistas estructuradas y pruebas para detectar infecciones de transmisiónsexual (ITS). Se compararon entre las dos ciudades las frecuencias de factoresindividuales y ambientales, como el abuso policial, el riesgo de infección por el VIH ylas conductas protectoras, usando regresión logística de una sola variable.Resultados. De 624 mujeres, casi la mitad comunicaron la confiscación de jeringaspor la policía a pesar de que es legal poseerlas; 55,6% informaron extorsión (en losúltimos 6 meses), con proporciones significativamente mayores en Ciudad Juárez(P < 0,001). Los informes de solicitación reciente de favores sexuales (28,5% en Tijuana,36,5% en Ciudad Juárez, P = 0,04) y de abuso sexual (15,7% en Tijuana, 18,3%en Ciudad Juárez) por la policía fueron comunes. La prevalencia de ITS fue significativamentemenor en Tijuana que en Ciudad Juárez (64,2% y 83,4%, P < 0,001), en formaanáloga a la menor prevalencia de conductas sexuales de riesgo en la primera ciudad.Las mujeres entrevistadas en Ciudad Juárez informaron una mediana del número declientes mensual significativamente mayor (6,8 frente a 1,5, P < 0,001) y una medianadel pago por acto sexual menor (US$ 10 frente a US$ 20, P < 0,001) en el último mes.En el último año, las mujeres entrevistadas percibieron un mayor aumento del desplieguede seguridad, especialmente la presencia del ejército, en Ciudad Juárez queen Tijuana (72,1% frente a 59,2%, P = 0,001).Conclusiones. Los daños colaterales derivados de las prácticas policiales en el contextodel conflicto de narcotráfico de México pueden afectar a la salud pública enla región de la frontera norte de México. Los oficiales itinerantes pueden facilitar lapropagación de enfermedades más allá de la región. Se analiza la urgencia para establecerintervenciones estructurales.

Identifying the HIV transmission bridge: which men are having unsafe sex with female sex workers and with their own wives or steady partners?

OBJECTIVE: To gain insights into bridging behaviors and their correlates among male clients of female sex workers (FSWs). METHODS: Men aged ≥18 years who recently paid or traded for sex with FSWs were recruited in Tijuana in 2008-2009. Participants underwent interviews and testing for HIV, chlamydia, syphilis, and gonorrhea. Logistic regression compared "bridgers" (clients who had unprotected sex with FSWs and with a wife or steady partner) with men who did not. RESULTS: Of 383 men, 134 (35%) had a steady partner. Half (n = 70) of those had unprotected sex with both FSWs and the steady partner. Prevalence of any sexually transmitted infection or HIV was 16.5% among bridgers and 2.3% among nonbridgers. Compared with other clients, bridgers were more likely to use drugs during sex with FSWs (81.4% versus 46.9%, P < 0.0001), had higher sensation-seeking (P < 0.0001) and misogyny scores (P = 0.05) and were more likely to offer FSWs extra money for unprotected sex (34.4% versus 1.6%, P < 0.0001). Factors independently associated with bridging were as follows: using drugs during sex with FSWs [adjusted odds ratio (AOR): 3.4, P = 0.007], sensation seeking (AOR: 4.3 per unit increase, P = 0.05), and offering FSWs more money for unprotected sex (AOR: 24.5, P = 0.003). CONCLUSION: Sensation-seeking clients who use drugs during sex and coerce FSWs into unprotected sex may be less responsive to standard risk reduction interventions. Interventions are needed that target clients rather than rely on FSWs to change behaviors that may not be under their control.

"Injection first": a unique group of injection drug users in Tijuana, Mexico.

Using baseline data from a study of injection drug users (IDUs) in Tijuana, Mexico (N = 1,052), we identified social and behavioral factors associated with injecting at the same age or earlier than other administration routes of illicit drug use (eg, "injection first") and examined whether this IDU subgroup had riskier drug using and sexual behaviors than other IDUs. Twelve-percent "injected first." Characteristics independently associated with a higher odds of "injection first" included being younger at first injection, injecting heroin as their first drug, being alone at the first injection episode, and having a sexual debut at the same age or earlier as when they initiated drug use; family members' illicit drug use was associated with lower odds of injecting first. When adjusting for age at first injection and number of years injecting, "injection first" IDUs had lower odds of ever overdosing, and ever trading sex. On the other hand, they were less likely to have ever been enrolled in drug treatment, and more commonly obtained their syringes from potentially unsafe sources. In conclusion, a sizable proportion of IDUs in Tijuana injected as their first drug using experience, although evidence that this was a riskier subgroup of IDUs was inconclusive.

Cigarette-Smoking Intensity and Interferon-Gamma Release Assay Conversion among Persons Who Inject Drugs: A Cohort Study.

We analyzed data from a longitudinal cohort study of persons who inject drugs (PWID) in Tijuana, Mexico, to explore whether cigarette smoking increases the risk of interferon gamma release assay (IGRA) conversion. PWID were recruited using respondent driven sampling (RDS). QuantiFERON-TB Gold In-Tube (QFT) assay conversion was defined as interferon-gamma concentrations <0.35 IU/mL at baseline and ≥0.7 IU/mL at 18 months. We used multivariable Poisson regression adjusted for RDS weights to estimate risk ratios (RRs). Of 129 eligible participants, 125 (96.9%) smoked at least one cigarette during followup with a median of 11 cigarettes smoked daily, and 52 (40.3%) had QFT conversion. In bivariate analysis, QFT conversion was not associated with the number of cigarettes smoked daily (P = 0.716). Controlling for age, gender, education, and alcohol use, the RRs of QFT conversion for smoking 6-10, 11-15, and ≥16 cigarettes daily compared to smoking 0-5 cigarettes daily were 0.9 (95% confidence interval (CI), 0.5-1.6), 0.5 (95% CI, 0.3-1.2), and 0.7 (95% CI, 0.3-1.6), respectively. Although this study did not find an association between self-reported smoking intensity and QFT conversion, it was not powered sufficiently to negate such an association. Larger longitudinal studies are needed to fully explore this relationship.

Male injection drug users try new drugs following U.S. deportation to Tijuana, Mexico.

BACKGROUND: Among male injection drug users (IDUs) in Tijuana, Mexico, U.S. deportation is associated with HIV transmission. Changing drug use behaviors following deportation, including the use of new drugs, may increase HIV risk but are understudied. We identify correlates of trying new drugs following male IDUs' most recent U.S. deportation to Mexico. METHODS: In 2010, we recruited 328 deported male IDUs in Tijuana, Mexico. Questionnaires collected retrospective data on drug use and other HIV risk behaviors throughout migratory events. Logistic regression identified correlates of trying new drugs/combinations following their most recent deportations. Informed consent was obtained from all participants. RESULTS: Nearly one in six men (n=52, 16%) tried new drugs following their most recent deportation, including heroin (n=31), methamphetamine (n=5), and heroin/methamphetamine combined (n=17). Trying new drugs following deportation was independently associated with U.S. incarceration (adjusted odds ratio [AOR]=3.96; 95% confidence interval [C.I.] 1.78, 8.84), increasing numbers of U.S. deportations (AOR=1.11 per deportation; C.I. 1.03, 1.20), feeling sad following deportation (AOR 2.69; C.I. 1.41, 5.14), and perceiving that one's current lifestyle increases HIV/AIDS risk (AOR 3.91; C.I. 2.05, 7.44). CONCLUSIONS: Trying new drugs following U.S. deportation may be related to the unique contexts and stressors experienced by drug-abusing migrants as they attempt to reestablish their lives in Mexico. Findings imply an unmet need for health and social programs to alleviate pre- and post-deportation stressors faced by undocumented and return migrants in the U.S.-Mexico context.

A comparison of registered and unregistered female sex workers in Tijuana, Mexico.

OBJECTIVE: Sex work is regulated in Tijuana, Mexico, but only half of the city's female sex workers (FSWs) are registered with the municipal health department, which requires regular screening for sexually transmitted infections (STIs) and human immunodeficiency virus (HIV). We examined correlates of registration to determine if it confers measurable health benefits. METHODS: From 2004 to 2006, we interviewed FSWs in Tijuana > or = 18 years of age who reported recent unprotected sex with at least one client and were not knowingly HIV-positive, and tested them for HIV, syphilis, gonorrhea, and chlamydia. Logistic regression identified factors associated with registration. RESULTS: Of 410 FSWs, 44% were registered, 69% had been tested for HIV, 6% were HIV-positive, and 44% tested positive for any STI. Compared with unregistered FSWs, registered FSWs were more likely to have had HIV testing (86% vs. 56%, p < 0.001) and less likely to test positive for any STI (33% vs. 53%, p < 0.001) or HIV (3% vs. 8%, p = 0.039). Factors independently associated with registration included ever having an HIV test (adjusted odds ratio [AOR] = 4.19) and earning > $30 per transaction without a condom (AOR = 2.41), whereas working on the street (AOR = 0.34), injecting cocaine (AOR = 0.06), snorting or smoking methamphetamine (AOR = 0.27), and being born in the Mexican state of Baja California (AOR = 0.35) were inversely associated with registration. CONCLUSION: Registered FSWs were more likely than unregistered FSWs to have had HIV testing and to engage in less drug use, but did not have significantly lower HIV or STI prevalence after adjusting for confounders. Current regulation of FSWs in Tijuana should be further examined to enhance the potential public health benefits of registration.

High prevalence of abscesses and self-treatment among injection drug users in Tijuana, Mexico.

BACKGROUND: Soft tissue infections are common among injection drug users (IDUs), but information on correlates and treatment in this highly marginalized population is lacking. METHODS: Six hundred twenty-three community-recruited IDUs in Tijuana, Mexico, completed a detailed interview on abscess history and treatment. Univariate and multiple logistic regressions were used to identify factors independently associated with having an abscess in the prior 6 months. RESULTS: Overall, 46% had ever had an abscess and 20% had had an abscess in the past 6 months. Only 12% had sought medical care for their most recent abscess; 60% treated the abscess themselves. The most common self-treatment method was to apply heated (24%) or unheated (23%) Aloe vera leaf. Other methods included draining the wound with a syringe (19%) or knife (11%). Factors independently associated with recent abscess were having income from sex work (adjusted odds ratio (aOR) 4.56, 95% confidence interval (CI) 2.08-10.00), smoking methamphetamine (aOR 1.65, 95% CI 1.05-2.62), seeking someone to help with injection (aOR 2.06, 95% CI 1.18-3.61), and reporting that police affected where they used drugs (aOR 2.14, 95% CI 1.15-3.96). CONCLUSIONS: Abscesses are common among IDUs in this setting, but appropriate treatment is rare. Interventions to reduce barriers to medical care in this population are needed. Research on the effectiveness of Aloe vera application in this setting is also needed, as are interventions to provide IDU sex workers, methamphetamine smokers, and those who assist with injection with the information and equipment necessary to reduce abscess risk.

Latent tuberculosis among persons at risk for infection with HIV, Tijuana, Mexico.

Because there is little routine tuberculosis (TB) screening in Mexico, the prevalence of latent TB infection (LTBI) is unknown. In the context of an increasing HIV epidemic in Tijuana, Mexico, understanding prevalence of LTBI to anticipate emergence of increased LTBI reactivation is critical. Therefore, we recruited injection drug users, noninjection drug users, female sex workers, and homeless persons for a study involving risk assessment, rapid HIV testing, and TB screening. Of 503 participants, the overall prevalences of TB infection, HIV infection, and TB/HIV co-infection were 57%, 4.2%, and 2.2%, respectively; no significant differences by risk group (p>0.05) were observed. Two participants had TB (prevalence 398/100,000). Incarceration in Mexico (odds ratio [OR] 2.28), age (OR 1.03 per year), and years lived in Tijuana (OR 1.02 per year) were independently associated with TB infection (p<0.05). Frequent LTBI in marginalized persons may lead to increases in TB as HIV spreads.

Polydrug use among IDUs in Tijuana, Mexico: correlates of methamphetamine use and route of administration by gender.

Tijuana is situated on the Mexico-USA border adjacent to San Diego, CA, on a major drug trafficking route. Increased methamphetamine trafficking in recent years has created a local consumption market. We examined factors associated with methamphetamine use and routes of administration by gender among injection drug users (IDUs). From 2006-2007, IDUs > or =18 years old in Tijuana were recruited using respondent-driven sampling, interviewed, and tested for HIV, syphilis, and TB. Logistic regression was used to assess associations with methamphetamine use (past 6 months), stratified by gender. Among 1,056 participants, methamphetamine use was more commonly reported among females compared to males (80% vs. 68%, p < 0.01), particularly, methamphetamine smoking (57% vs. 34%; p < 0.01). Among females (N = 158), being aged >35 years (AOR, 0.2; 95% CI, 0.1-0.6) was associated with methamphetamine use. Among males (N = 898), being aged >35 years (AOR, 0.5; 95% CI, 0.3-0.6), homeless (AOR, 1.4 (0.9-2.2)), and ever reporting sex with another male (MSM; AOR, 1.9; 95% CI, 1.4-2.7) were associated with methamphetamine use. Among males, a history of MSM was associated with injection, while sex trade and >2 casual sex partners were associated with multiple routes of administration. HIV was higher among both males and females reporting injection as the only route of methamphetamine administration. Methamphetamine use is highly prevalent among IDUs in Tijuana, especially among females. Routes of administration differed by gender and subgroup which has important implications for tailoring harm reduction interventions and drug abuse treatment.

Estimaciones de prevalencia del VIH por género y grupo de riesgo en Tijuana, México: 2006 / Estimating the 2006 prevalence of HIV by gender and risk groups in Tijuana, Mexico

Objetivo: Estimar la prevalencia para 2006 de HIV/sida entre población general de 15 a 49 años de edad y en los grupos de riesgo, en la ciudad de Tijuana, México. Métodos: Se obtuvieron datos demográficos del censo mexicano de 2005 y la prevalencia del VIH, de la literatura. Se construyó un modelo de prevalencia del VIH para la población general y de acuerdo con el género. El análisis de sensibilidad consistió en estimar los errores estándar del promedio-ponderado de la prevalencia del VIH y tomar derivados parciales respecto a cada parámetro. Resultados: La prevalencia del VIH resultó ser de 0.54% (N = 4,347) (rango 0.22-0.86% [N = 1750-6944]). Esto sugiere que 0.85% (rango 0.39-1.31%) de los hombres y 0.22% (rango 0.04-0.40%) de las mujeres podrían ser VIH-positivos. Los hombres que tienen sexo con hombres, las mujeres trabajadoras sexuales usuarias de drogas inyectables (UDI), las mujeres trabajadoras sexuales-no UDI, mujeres- UDI y los hombres-UDI, contribuyeron a las proporciones más elevadas de personas infectadas por el VIH. Conclusiones: El número de adultos VIH-positivos entre subgrupos de riesgo en la población de Tijuana es considerable, lo que denota la necesidad de enfocar las intervenciones de prevención en sus necesidades específicas. El presente modelo estima que hasta uno de cada 116 adultos podría ser VIH-positivo.

OBJECTIVE: Estimate the 2006 HIV prevalence among adults aged 15-49 from the general population and at-risk subgroups in Tijuana, Mexico. METHODS: Demographic data was obtained from the 2005 Mexican census and HIV prevalence data was obtained from reports in the literature. We developed a population-based HIV prevalence model for the overall population and stratified it by gender. Sensitivity analysis consisted of estimating standard errors in the weighted-average point prevalence and calculating partial derivatives of each parameter. RESULTS: HIV prevalence among adults was 0.54% (N = 4347) (range 0.22-0.86% [N = 1750-6944]). This suggests that 0.85% (range 0.39-1.31%) of men and 0.22% (0.04-0.40%) of women could have been HIV-infected in 2006. Men who have sex with men (MSM), followed by female sex workers who are injection drug users (FSW-IDU), FSW-non IDU, female IDU, and male IDU were the most at risk groups of infected individuals. CONCLUSIONS: The number of HIV-infected adults among at-risk subgroups in Tijuana is significant, highlighting the need to design tailored prevention interventions that focus on the specific needs of certain groups. According to our model, as many as 1 in 116 adults could potentially be HIV-infected.

Prevalence and correlates of HIV infection among female sex workers in 2 Mexico-US border cities.

BACKGROUND: We examined human immunodeficiency virus (HIV) prevalence and correlates among female sex workers (FSWs) in Tijuana and Ciudad Juarez, 2 large cities on the Mexico-US border. METHODS: FSWs aged > or =18 years underwent interviews and testing for HIV, syphilis, gonorrhea, and chlamydia. Logistic regression identified factors associated with HIV infection. RESULTS: In 924 FSWs, the prevalence of HIV, gonorrhea, chlamydia, and syphilis titers > or =1:8 was 6%, 6.4%, 13%, and 14.2%, respectively. Factors independently associated with HIV were the injection of cocaine (odds ratio [OR], 2.96); the smoking, snorting, or inhalation of methamphetamine (OR, 3.32); and syphilis titers > or =1:8 (OR, 4.16). CONCLUSIONS: Culturally appropriate interventions are needed to identify and treat ulcerative sexually transmitted infections and reduce HIV risks associated with stimulants among FSWs in the Mexico-US border region.

Barriers and missed opportunities to HIV testing among injection drug users in two Mexico--US border cities.

INTRODUCTION AND AIMS: Despite increasing HIV prevalence in cities along the Mexico--US border, HIV testing among high-risk populations remains low. We sought to identify barriers associated with HIV testing among injection drug users (IDUs) in Tijuana and Ciudad Juarez, the two largest Mexican border cities located across from San Diego, California and El Paso, Texas, respectively. DESIGN AND METHODS: In 2005, 222 IDUs in Tijuana and 205 IDUs in Ciudad Juarez were recruited by respondent-driven sampling and administered a questionnaire to collect socio-demographic, behavioural and HIV testing history data. Blood samples were provided for serological testing of HIV, hepatitis C virus (HCV) and syphilis. RESULTS: Only 38% and 30% of respondents in Tijuana and Ciudad Juarez, respectively, had ever had an HIV test. The factors independently associated with never having been tested for HIV differed between the two sites, except for lack of knowledge on HIV transmission, which was independently associated in both locales. Importantly, 65% of those who had never been tested for HIV in both cities experienced at least one missed opportunity for voluntary testing, including medical visits, drug treatment and spending time in jail. DISCUSSION AND CONCLUSIONS: Among this high-risk IDU population we found HIV testing to be low, with voluntary testing in public and private settings utilised inadequately. These findings underscore the need to expand voluntary HIV education and testing and to integrate it into services and locales frequented by IDUs in these Mexico--US border cities.

Prevalence of hepatitis C virus and HIV infection among injection drug users in two Mexican cities bordering the U. S

OBJECTIVE: To estimate the prevalence of the hepatitis C virus (HCV) and HIV infection and associated risk behaviors among injection drug users (IDUs) in two northern Mexican cities. MATERIAL AND METHODS: Between February and April 2005, IDUs were recruited in Tijuana (N=222) and Ciudad Juarez (N=206) using respondent-driven sampling (RDS), a chain referral sampling approach. Interviewer-administered questionnaires assessed drug-using behaviors during the prior six months. Venous blood was collected for immunoassays to detect HIV and HCV antibodies. For HIV, Western blot or immunofluorescence assay was used for confirmatory testing. Final HCV antibody prevalence was estimated using RDS adjustments. RESULTS: Overall, HCV and HIV prevalence was 96.0 percent and 2.8 percent, respectively, and was similar in both cities. Most IDUs (87.5 percent) reported passing on their used injection equipment to others, and 85.9 percent had received used equipment from others. CONCLUSIONS: HIV prevalence was relatively high given the prevalence of HIV in the general population, and HCV prevalence was extremely high among IDUs in Tijuana and Ciudad Juarez. Frequent sharing practices indicate a high potential for continued transmission for both infections. HCV counseling and testing for IDUs in Mexico and interventions to reduce sharing of injection equipment are needed.

OBJETIVO: Estimar las prevalencias de los virus de hepatitis C (VHC) y de VIH y los comportamientos de riesgo asociados con ellos, entre usuarios de drogas inyectables (UDI) en dos ciudades del norte de México. MATERIAL Y MÉTODOS: Entre febrero y abril de 2005, se reclutaron UDIs en Tijuana (N=222) y en Ciudad Juárez (N=206), mediante un método de muestreo llamado en inglés "respondent-driven sampling" (RDS), lo cual es un sistema basado en cadenas de referencia. Los participantes contestaron una encuesta aplicada por entrevista, la cual indagó acerca de los comportamientos en el uso de drogas durante los seis meses previos. Una muestra de sangre venosa fue colectada de cada individuo, para determinar la presencia de anticuerpos contra VIH y VHC mediante técnicas inmunoenzimáticas. En el caso del VIH la técnica de "Western blot" se aplicó con fines de confirmación. La prevalencia final de anticuerpos contra VHC se hizo mediante un cálculo ajustado, que empleó un estimador poblacional del RDS. RESULTADOS: Las seroprevalencias globales de VHC y VIH, fueron 96 por ciento y 2.8 por ciento, respectivamente. Estas frecuencias fueron similares entre las muestras de ambas ciudades. La gran mayoría de los UDI (87.5 por ciento) manifestó haber transferido a otros sus equipos de inyección usados y a su vez 85.9 por ciento de los participantes declaró haber recibido equipos usados de otros. CONCLUSIONES: La seroprevalencia encontrada de VIH fue relativamente alta dada la prevalencia de VIH en la población general y la de VHC fue extremadamente alta entre los UDI estudiados en Tijuana y en Ciudad Juárez. Las prácticas frecuentes de compartimiento de equipo señalan hacia un alto potencial que favorece la transmisión de ambas infecciones investigadas. Por tanto, son necesarias actividades de consejería y pruebas de laboratorio para VHC dirigidas a UDI en México y asimismo intervenciones para reducir el uso compartido de equipos de inyección.

Respondent-driven sampling of injection drug users in two U.S.-Mexico border cities: recruitment dynamics and impact on estimates of HIV and syphilis prevalence.

Respondent-driven sampling (RDS), a chain referral sampling approach, is increasingly used to recruit participants from hard-to-reach populations, such as injection drug users (IDUs). Using RDS, we recruited IDUs in Tijuana and Ciudad (Cd.) Juárez, two Mexican cities bordering San Diego, CA and El Paso, TX, respectively, and compared recruitment dynamics, reported network size, and estimates of HIV and syphilis prevalence. Between February and April 2005, we used RDS to recruit IDUs in Tijuana (15 seeds, 207 recruits) and Cd. Juárez (9 seeds, 197 recruits), Mexico for a cross-sectional study of behavioral and contextual factors associated with HIV, HCV and syphilis infections. All subjects provided informed consent, an anonymous interview, and a venous blood sample for serologic testing of HIV, HCV, HBV (Cd. Juárez only) and syphilis antibody. Log-linear models were used to analyze the association between the state of the recruiter and that of the recruitee in the referral chains, and population estimates of the presence of syphilis antibody were obtained, correcting for biased sampling using RDS-based estimators. Sampling of the targeted 200 recruits per city was achieved rapidly (2 months in Tijuana, 2 weeks in Cd. Juárez). After excluding seeds and missing data, the sample prevalence of HCV, HIV and syphilis were 96.6, 1.9 and 13.5% respectively in Tijuana, and 95.3, 4.1, and 2.7% respectively in Cd. Juárez (where HBV prevalence was 84.7%). Syphilis cases were clustered in recruitment trees. RDS-corrected estimates of syphilis antibody prevalence ranged from 12.8 to 26.8% in Tijuana and from 2.9 to 15.6% in Ciudad Juárez, depending on how recruitment patterns were modeled, and assumptions about how network size affected an individual's probability of being included in the sample. RDS was an effective method to rapidly recruit IDUs in these cities. Although the frequency of HIV was low, syphilis prevalence was high, particularly in Tijuana. RDS-corrected estimates of syphilis prevalence were sensitive to model assumptions, suggesting that further validation of RDS is necessary.