Directors' Choice


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Oct.  2018 Mehta SR, Chaillon A, Gaines TL, Gonzalez-Zuniga PE, Stockman JK, Almanza-Reyes H, Chavez JR, Vera A, Wagner KD, Patterson TL, Scott B, Smith DM, Strathdee SA. Impact of Public Safety Policies on Human Immunodeficiency Virus Transmission Dynamics in Tijuana, Mexico. Clin Infect Dis. 2018 Feb 10;66(5):758-764. PMID: 29045592 PMCID: 5848227

About This Paper

Tijuana, Mexico has a thriving “red light” district and dynamic illicit drug market, which have contributed to the one of the highest rates of HIV in Mexico. In 2015, the Mexican government began to expand the San Ysidro border crossing between the United States and Mexico, and as part of these efforts began to “clean” the homeless population from the Tijuana River and canal basin (locally called El Bordo) to improve “public safety”. This was accomplished by orchestrated police raids and patrols, and bulldozing of erected dwellings in the area. Many residents were sent to rehabilitation facilities, often involuntarily. Those who wished to avoid placement in rehabilitation facilities were forced to move, and the canal was made inaccessible to pedestrians. We hypothesized that this dispersal of high-risk individuals and disruption of prevention efforts would change the dynamics of HIV transmission in the region. 


Examining data collected from 8 research studies in Tijuana which screened for and collected data on HIV infection, we used passive sampling to evaluate the regional HIV epidemic in near real time.  These studies included individuals from multiple risk groups including male clients of FSWs (Amigos and Hombre Seguro), FSWs (Mujer Segura), injection drug–using FSWs (Mujer Mas Segura), FSWs and their noncommercial partners (Proyecto Parejas), a historical study of HIV-infected individuals in Tijuana (Study of HIV Drug Resistance), MSM (Enlaces), prison inmates (La Mesa Health Study), and PWID (Proyecto El Cuete IV [EC]). Using HIV sequence data from 288 sampled individuals we inferred the regional transmission network.  We found a cluster of PWID that included several seroconverters, suggesting recent transmission events.  We also found an increase in seroconversions overall in mid 2016. We went back and performed qualitative interviews on these individuals and found a common theme of needing to relocate the location of residence and injection drug used after the public safety intervention.


In summary, our molecular epidemiologic analysis demonstrated clustering of recent seroconversion in PWID as well as an overall uptick.  Using qualitative interviewing we determined that these clusters and the uptick in seroconversions was associated with a shift in injection drug use locations. This shift was likely associated with an increased risk of high-risk IDU due to displacement from harm reduction services and disruption of social networks. Thus, we found that well-intentioned changes in policy toward high-risk homeless and PWID living in the border region, and efforts to relocate and involuntarily commit individuals to rehabilitation, has driven some high-risk behaviors underground, where neither the government nor NGOs are able to provide adequate harm reduction support (ie, needle exchange services), leading to increased risk-taking behavior (ie, needle sharing), resulting in the observed outbreak.

View other Directors' Choice selections from 2018,  2017, and  2016.

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