US, Mexican Border Restrictions Did Not Reduce HIV Infection

The spread of human immunodeficiency virus 1 (HIV-1) infections increased despite restrictions on the border between Mexico and the United States during the COVID-19 pandemic, according to a prospective cohort study of users of unregulated injectable drugs in the cities of Tijuana, Mexico, and San Diego, California.

The findings of this study, which was led by researchers from the University of California in San Diego and Irvine, California, show that measures to restrict traffic across Mexico’s northern border were counterproductive, as efforts to contain the spread of COVID-19 resulted in an increase in HIV-1 transmission among injectable drug users.

“Our analysis showed that the HIV epidemics in Tijuana and San Diego are intertwined and that border closure did not impact frequent viral mixing between the two municipalities,” wrote the researchers in an article published in The Lancet Regional Health – Americas.

“Indeed, we found evidence of growth for one of the large clusters at the border…and did not find evidence of decline for the other,” they added. The researchers used phylogenetic analysis to identify local transmission clusters, including genome sequences of the virus from 45 of the 49 injectable drug users with HIV-1 at the study’s onset. They identified 16 clusters that included at least one sequence belonging to the cohort.

“The overall aim is based on the observation that there was considerable transit of people across the border for drug use, and we thought this might influence HIV-1 transmission,” study author Britt Skaathun, PhD, an epidemiologist at the Division of Infectious Diseases and Global Public Health at the University of California, San Diego, told the Medscape Spanish edition. “Our results were surprising as they contradict the belief that closing borders would reduce transmission.”

“It is a very revealing study as it provides compelling data on how HIV-1 infections increased during the border closure in these communities, which are most vulnerable to this infection and others, such as hepatitis C. They are more vulnerable, especially on this side of the border,” said Clara Fleiz Bautista, a psychologist and researcher in medical sciences at the National Institute of Psychiatry in Mexico City, Mexico.

The team of experts recruited 622 individuals aged > 18 years from three groups: Residents of San Diego who crossed the border to obtain drugs in Tijuana, as well as residents of both cities who did not have to cross for the same purpose. They recorded the baseline HIV-1 prevalence (8%) and bivariate incidence density rates at 18 months. Finally, they applied phylogenetic analysis to identify local transmission clusters, estimate their age and effective reproduction number.

In the group of San Diego residents who crossed the border to inject drugs in Tijuana, the prevalence rate of HIV-1 was 4%. This same prevalence rate was observed among drug users residing in San Diego who reported not crossing the border to consume drugs, while in the group of Tijuana residents who also did not cross the border to use substances, the prevalence rate of HIV-1 was 16%.

Among participants who attended a follow-up visit at 18 months and underwent an HIV-1 test, nine seroconversions were identified, with an incidence rate of 1.36 (95% CI; 0.47-2.24). The HIV-1 incidence rate was significantly higher among Tijuana residents compared with that in San Diego residents who did not cross the border (difference in incidence rate, 0.03%) and in relation to those who left this city (incidence rate ratio, 3.82; difference in incidence rate, 2.12).

Another relevant finding, as highlighted by Skaathun, was that the HIV-1 incidence varied significantly by gender and sexual orientation. The rate was 2.36 among cisgender women, 0.82 among cisgender men, 21.7 among transgender and nonbinary individuals, 1.23 among heterosexual individuals, and 7.9 among individuals identifying as gay, lesbian, or transgender individuals.

Mexicans Vulnerable

Fleiz warned that cases of HIV-1 among injectable drug users near Mexico’s northern border have increased, as documented in ongoing research she coordinates to determine the prevalence of infectious diseases among these border populations. She and her team noted that HIV-1 prevalence in in Tijuana increased from 4.5% to 12.0% between 2019 and 2023, a figure very close to what Skaathun and her collaborators found (16.0%).

“We observed an upward trend in these same communities in Tijuana during and after the pandemic. We noticed that beyond the border closure, the structural conditions continue to prevail that disadvantage these vulnerable communities, such as barriers to accessing harm reduction services due to public policies that reduced budgets for organizations that provide support and overall, for the health sector,” said Fleiz.

During the pandemic, many civil organizations have faced difficulties in obtaining the necessary supplies to mitigate harm, such as needles for exchange in the case of opioid or methamphetamine-type stimulant injectable drug users, she added. Moreover, there were complications in crossing the border to acquire these supplies, which are often donations from organizations in the United States that supply needles or naloxone to these Mexican populations.

So far, naloxone, the opioid antagonist drug considered a psychotropic and used to treat the most dangerous effects of overdose from these substances, is not deregulated in the General Health Law. For that reason, it must be imported from the United States with special permits, along with the regular request for other supplies.

Skaathun acknowledged that her study did not collect data on the differences in the quality of healthcare services that patients receive on either side of the border. “We know there was a shortage of resources during the COVID-19 pandemic for several reasons.” The most notable of these reasons, as she specified, was the change in systems to receive care. “Due to the pandemic, people seeking access to health services required appointments. This system was also implemented for harm-reduction services and clinics providing methadone on both sides of the border, significantly impacting the number of users who could be attended to.”

At-Risk Populations

In Mexico, according to the National Center for the Prevention and Control of HIV and AIDS (CENSIDA), the incidence of this virus in the general population was 0.16 per 1000 inhabitants (around 20,000 new infections) until 2022. This represented a 13% increase compared with 2010, although the trend has been stable since 2019.

In the general population, the prevalence of HIV-1 has been estimated at 0.3% for 2022, meaning that three out of every 1000 Mexicans had this infection, according to CENSIDA. The disease is concentrated in certain populations: Men who have sex with men (12.4% prevalence), male sex workers (6.1%), transgender women (8.2%), and female sex workers (1.3%).

Fleiz added that another risk factor that increases the vulnerability of these “key” populations, as CENSIDA calls them, is the use, mostly unnoticed, of drugs adulterated with substances that increase their addictive potential and their lethality, such as fentanyl or xylazine, a nonopioid analgesic approved only for veterinary use in Mexico and the United States.

“With these adulterants, drug users enter a deeper state of sedation, which is precisely what they seek to alleviate the pain and discomfort caused by withdrawal syndrome. The issue is that by doing so, they may incur more overdoses, and if we already have a problem with fentanyl — in their study, they found this substance in six out of every 10 heroin samples — xylazine comes to complicate it even further,” said Fleiz.

These border communities are also highly vulnerable to other health complications besides HIV-1, such as hepatitis C, worsening tuberculosis, heart attacks caused by overdoses, and skin abscesses, said Fleiz. “Although there are other contextual factors, such as lack of access to water, scientific evidence points to a relationship between xylazine and skin lesions, as the intravenous adulterant breaks capillary barriers.”

Therefore, it is necessary to address these issues not only as a matter of national security but also to focus on the health problems that these individuals face, said Fleiz. The goal is to eliminate the social stigma weighing on these patients and implement public policies that can affect the socioeconomic factors forcing them to live on the streets, where they cannot address their basic needs or access health services.

“These key populations, to which migrants should also be added, are one of the groups where inequality has reached its extreme on the bottom rung of the social ladder. Unfortunately, they are the most stigmatized, most criminalized, with more health problems, and with more barriers to access treatments,” said Fleiz.

The research conducted by the University of California received financial support from the James B. Pendleton Charitable Trust and the San Diego Center for AIDS Research in San Diego. Skaathun and Fleiz Bautista declared no relevant financial conflicts of interest.

This story was translated from the Medscape Spanish edition using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.