Closing the border doesn’t prevent HIV from spreading

Rather than preventing the spread of disease, closing the border between San Diego, California, and Tijuana, Mexico, during the COVID-19 pandemic increased the rate of HIV transmission, says a study co-authored by Branco Weiss Fellow Tetyana Vasylyeva and others published recently in the journal The Lancet regional health – Americas. The reason for this unintuitive finding: the ongoing drug tourism from San Diego to Tijuana.

To investigate the dynamics between border closure, drug use and HIV transmission, the researchers studied 618 participants from October 2020 to October 2021. Combining molecular epidemiology with the answers from questionnaires, the scientists found that people were crossing the border in both directions and being exposed to HIV despite government efforts to keep the border closed. The scientists applied advanced molecular techniques to investigate how closely the viruses were related genetically and to estimate the timing of cross-border HIV transmission. They found that during the 18-month period of their study, nine people contracted HIV, mostly during the pandemic – a high number for the U.S., where HIV incidence is relatively low. And to their surprise, all of the new clusters had sequences from participants on both sides of the border, indicating that cross-border transmission was happening right when the border was closed.

“Our results demonstrate that efforts to end the HIV epidemic in the U.S. should take into account cross-border HIV-1 transmission from Tijuana,” the authors write in the paper, calling for mobile harm reduction services (i. e. the provision of syringes and HIV testing) on both sides of the border and an improved coordination with local HIV prevention programs.

Read the paper in The Lancet regional health – Americas

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