Drug Tourism to Mexico: Impact of New Drug Law on HIV/HCV/TB Infection on US Injection Drug Users (2011-2016)


Funded by: NIH/NIDA, grant 1R01DA031074; PI: Richard S. Garfein, PhD, MPH

On August 20th, 2009, Mexico enacted legislation decriminalizing possession of small amounts of psychoactive drugs for personal use, including methamphetamine, cocaine, heroin, marijuana and LSD. However, possession of illicit substances remains illegal in the United States, eliciting concern that U.S. drug users will travel to Mexico to purchase and use illegal drugs. San Diego, which shares the busiest land border crossing in the world with Tijuana, B.C., Mexico, may be at an increased risk for such “drug tourism”, thereby facilitating interaction between people who inject drugs (PWID) from both countries. Previous studies estimate that 21% of San Diego PWID have ever injected drugs in Mexico. An estimated 95% of PWID in Tijuana have been infected with hepatitis C virus (HCV), compared to 25% among PWID in San Diego. Additionally, two-thirds of PWID in Tijuana test positive for M. tuberculosis (Mtb) infection compared with 10%-20% of San Diegan PWID. These findings suggest that increased mixing between PWID from both countries could increase incident HCV and Mtb infection in San Diego PWID. The goal of this study was to examine the change in knowledge, attitudes (risk perceptions) and practices over time among PWID residing in San Diego and to assess PWID’s behaviors and HCV, Mtb, and HIV infection status over time subsequent to the change in Mexico’s drug laws.  The study used a mixed-methods design involving quantitative and qualitative data collection.  Quantitative methods include recruiting a cohort of 579 PWID in San Diego for a baseline and 4 semi-annual follow-up visits that included behavioral assessments and serologic testing for HIV, HCV, and Mtb infections over a 24-month period. Qualitative methods involved selecting 20 participants after each of the assessment visits (total=48) for in-depth interviews and one member checking focus group (total=19).  Interviews were designed to explore the sociocultural context of drug use in Mexico, including participants’ attitudes and beliefs, in order would both inform and explain the quantitative results.  This study had the following aims:

• Aim 1: To identify sociodemographic, behavioral, and serologic differences between PWID in San Diego who do and do not inject in Mexico
• Aim 2: To describe how changes in knowledge, attitudes and perceptions about injecting drugs in Mexico influence behaviors among San Diego PWID over time since Mexico’s drug law changed.
• Aim 3: To determine whether PWID from San Diego who inject in Mexico are at increased risk for incident HCV and Mtb infection compared to PWID who do not inject in Mexico.

Research Collaborations
As part of the mission of the Division of Global Public Health to initiate, participate and foster collaborations on global health activities within and across departments across UCSD, the UC system and U.S.-based and international governmental and non-governmental agencies and institutions; STAHR II emphasized efforts in academic and research collaborations.  Such efforts included training opportunities, data sharing plans, and design and questionnaire development. An example of this was that the STAHR II and Proyecto El Cuete (NIDA R37DA019829; PI: S. Strathdee) were designed to have comparable data of their study populations by aligning the studies questionnaires and eligibility criteria’s.  By doing so, the potential to compare PWID between San Diego, CA and Tijuana, Mexico is of great potential.

STAHR-II data are also being used as part of a multi-site study (US, Mexico, Canada, France) seeking to identify structural-level factors that increase the risk that people who inject drugs (PWID) will initiate others into injecting (NIDA Avenir Award DP2-DA040256-01; PI: D. Werb).  Data from STAHR-II are integral to determining the impact of macro-level policy changes in California (i.e., reclassification of drug possession as a misdemeanor rather than a felony) on injection initiation risk. Inclusion of the STAHR-II cohort within Dr. Werb’s PRIMER study allows for a range of potentially high impact secondary data analyses, as well as for the recruitment of graduate and postdoctoral trainees to work with these data.

Opportunities for collaboration using STAHR II data or stored specimens can be directed to Richard Garfein (rgarfein@ucsd.edu)

Principal Investigator: Richard S. Garfein, PhD, MPH

Collaborators: Peter Chiles, Sergio Aguilar-Gaxiola, Kathleen Moser, Avelardo Valdez, Alfredo Velasco.

Project Coordinator: Jazmine Cuevas-Mota

Research Team: Everardo Aguilar, Richard Armenta, Jose Luis Burgos, Kelly Collins, Daniel Goba, Erik Hendrickson, Danielle Horyniak, Lin Liu, Natasha Ludwig-Barron Meredith Meacham, Fatima Muñoz, Antonio Muñoz, Victoria Ojeda, Alexandra Roth, Pilar Santamaria, Steffanie Strathdee, Carlos Vera, Karla Wagner, Daniel Werb,

1. Robertson A, Garfein RS, Wagner KD, Mehta SR, Magis-Rodriguez C, Cuevas-Mota J, G, Gonzalez Moreno-Zuniga P, Strathdee SA. Evaluating the impact of Mexico’s drug policy reforms on people who inject drugs in Tijuana, B.C., Mexico, and San Diego, CA United States: A binational mixed methods research agenda. Harm Reduction Journal, 2014;11:4. PMCID: PMC3944401.
2. Muñoz F, Burgos JL, Cuevas-Mota J, Teshale E, Garfein RS. Individual and socio-environmental factors associated with unsafe injection practices among young adult injection drug users in San Diego. AIDS and Behavior. 2014;19:199-2010 PMCID:    PMC4265001
3. Roth AM, Armenta RA, Wagner KD, Roesch SC, Bluthenthal RN, Cuevas-Mota J, Garfein RS. Patterns of drug use, risky behavior, and health status among persons who inject drugs living in San Diego, California: A latent class analysis. Substance Use and Misuse. 2015;50(2):205-14. PMCID:  PMC4356115.
4. Wagner KD, Armenta RF, Roth AM, Maxwell JC, Cuevas Mota J, Garfein RS. Use of synthetic cathinones and cannabimimetics among injection drug users in San Diego, California. Drug and Alcohol Dependence, 2014;141:99-106. PMCID: PMC4114932,
5. Wagner KD, Liu L, Davidson PJ, Cuevas-Mota J, Armenta RF, Garfein RS. Association between non-fatal opioid overdose and encounters with healthcare and criminal justice systems: Identifying opportunities for intervention. Drug and Alcohol Dependence. 2015;153:215-20. PMCID: PMC4512661.
6. Armenta RF, Roth AM, Wagner KD, Strathdee SA, Brodine SK, Cuevas-Mota J, Munoz FA, Garfein RS.  Prevalence and correlates of the use of prefilled syringes among persons who inject drugs in San Diego, CA. Journal of Urban Health. 2015 Dec;92(6):1081-91. PMCID: PMC4675744
7. Meacham MC, Armenta R, Garfein RS, Cuevas-Mota, J, Moreno-Zuniga PG, Strathdee S. Prevalence and correlates of heroin-methamphetamine co-injection among persons who inject drugs in San Diego, CA, USA and Tijuana, BC, Mexico. Drug and Alcohol Dependence. 2015 Nov Vol. 156:e148. PMCID: PMC5015469
8. Mehta SR, Wertheim JO, Brouwer KC, Wagner KD, Chaillon A, Strathdee S, Patterson TL, Rangel MG, Vargas M, Murrell B, Garfein RS, Little SJ, Smith DM. HIV transmission networks in the San Diego–Tijuana border region. EBioMedicine. 2015 Jul 18;2(10):1456-63. PMCID: PMC4634195
9. Collins KM, Armenta RF, Cuevas-Mota J, Liu L, Strathdee SA, Garfein RS. Factors Associated With Patterns of Mobile Technology Use Among Persons Who Inject Drugs. Substance Abuse. [Epub 2016 Apr 19]. PMID: 27092425
10. Werb D, Garfein R, Kerr T, Davidson P, Roux P, Jauffret-Roustide M, Auriacombe M, Small W, Strathdee S. A socio-structural approach to preventing injection drug use initiation: rationale for the PRIMER study. Harm Reduction Journal 2016;13:25. PMCID: PMC5024479.
11. Roth AM, Rossi J, Goldshear JL, Truong Q, Armenta RF, Lankenau SE, Garfein RS, Simmons J. Potential Risks of mHealth Research: An exploration of perceptions among persons who inject drugs. Substance Use and Misuse. (accepted)
12. Horyniak D, Wagner KD, Armenta RF, Cuevas-Mota J, Hendrickson E, Garfein RS. Cross-border injection drug use and HIV and hepatitis C virus seropositivity among people who inject drugs in San Diego, California. International Journal of Drug Policy. (Submitted)