COVID-19 creates new syndemic on US-Mexico border

July / August 2020 | Volume 19, Number 4

Woman wearing plastic gloves holds the arm (with many tatoos) of a man in front of a mobile health clinic.
Photo by Bob Ross, courtesy of UCSD

FILE - In this file photo, former Fogarty grantee Dr. Steffanie
Strathdee conducted research along the US-Mexico border
prior to the COVID-19 pandemic. She plans to use the
binational network built over the years to study COVID-19
transmission in the area.

By Susan Scutti

Border regions tend to be a “no man’s land,” where countries don’t pay the same level of attention and infectious diseases - including coronavirus - can run rampant, says NIH grantee Dr. Steffanie Strathdee. She recently received funding to study SARS-CoV-2 along the US-Mexico border, where the University of California, San Diego (UCSD) professor has been conducting research since 2004. If you were to conceptualize this area as a state, “it would be the poorest in every indicator of poverty and socioeconomic status,” said Strathdee. Not surprisingly the region experiences elevated rates of HIV, sexually transmitted infections and latent tuberculosis. With California a COVID-19 hotspot, pandemic monitoring along the border is critical.

Strathdee and her interdisciplinary team will collect pilot data to inform future research on pandemic transmission in the border zone, with a two-year grant supplement from the National Institute on Drug Abuse (NIDA). A study of viral shedding that involves testing nasal swabs and fecal smears for SARS-CoV-2 will be led by Dr. Jack Gilbert. This work will inform whether wastewater can be used for COVID-19 surveillance and whether harmful bacteria are hitching a ride with the pandemic virus.

Meanwhile, Dr. Antoine Chaillon, a molecular virologist on the team, will sequence SARS-CoV-2 isolates to establish a molecular clock. “By comparing sequences, you can establish timing and that will tell us the directionality of the infection - whether it’s going from north to south or south to north,” explained Strathdee. Understanding directionality would provide needed context for immigration, drug and health policies, she said. In addition, by comparing the genetic sequencing of the samples collected on the border with those in global databases, her team will be able to tell if different strains are circulating, which is important for the vaccine effort.

Fogarty funding for her earlier research training projects helped her build a binational network with longtime Mexican partners Drs. Gudelia Rangel and Carlos Magis-Rodriguez. This laid the foundation for her new research, said Strathdee, who is currently a member of Fogarty’s advisory board. By watching successful Fogarty grantees, she learned that establishing trust meant her Mexican collaborators inform decisions about which research questions will most effectively influence policies and programs south of the border.

Her NIDA parent grant Ethno-epidemiology of HCV, HIV and Overdose Associated with Drug Markets and Drug Tourism is funding an investigation of how drug policies influence behavior and health, particularly HIV transmission. The team includes Rangel and Dr. Annick Borquez, a Mexican researcher who recently received NIDA's Avenir award. In recent years, Mexico has become more permissive with drug possession laws, while the U.S. has become more stringent. As a result, San Diego users travel to Tijuana to buy and use drugs where drugs are cheaper and used more openly. “And, when you have a border closure like we’re experiencing now, there’s a backup of drugs in Tijuana and that also changes the drug market,” said Strathdee.

Such macrolevel political and economic factors often influence individual behavior, which in turn affects disease transmission, she explained. And so it’s an “open question” whether addiction predisposes people who inject drugs (PWID) to COVID-19. For example, they may not practice social distancing when seeking a fix. PWID who earn their living through sex work may be more willing to accept higher pay for unprotected sex because they have fewer clients with the decline in tourists to Mexico. Other behaviors documented when drugs are in short supply include non-injecting users turning to cost-effective injection or pooling money to purchase and then sharing needles. It’s possible the PWID border community may be a sentinel population for COVID-19 risk, noted Strathdee.

Uncovering social, political and economic drivers of infectious disease has long been a hallmark of Strathdee’s research. “We’ve been misplacing HIV prevention efforts by blaming individuals for their behavior - not using condoms or sharing needles, for example - when it’s really the underlying societal drivers that we create that put people at risk,” she said. Disrupting macrolevel factors could reduce rates of HIV, COVID-19 and multiple other diseases with similar root causes, she said. “It’s really about considering these infectious diseases as syndemics.”

NIDA also appreciates that “people are influenced by the social, political and economic influences around them” and has been “incredibly supportive” of her research, said Strathdee. Conducting research amid a pandemic poses challenges, including an indefinitely closed border, and the need for additional safety protocols and supplies. Also, ethics committees on both sides of the border must review and ensure appropriate reporting compliance, adding “a layer of complexity in the midst of an epidemic,” said Strathdee. Still, her team is on track to begin collecting data in August 2020.

Personal as well as professional experience guide Strathdee on this new project. In 2015, her husband, Dr. Tom Patterson, a psychiatry professor at UCSD, was dying from a multidrug-resistant bacterial infection. After numerous treatment failures, a desperate Strathdee pored over the scientific literature and discovered a forgotten cure, 100-year old bacteriophage therapy. With the help of a global village of researchers who donated phage, Patterson’s doctors transformed this into an experimental treatment and saved his life.

“Sometimes when your back is against the wall and you think you’ve run out of solutions, that is when your best creative moments arise,” said Strathdee. The silver lining of COVID-19 is that the challenge has driven researchers from different disciplines and multiple countries to work together. “When you do that, it’s an incubator for innovation,” said Strathdee. “And that gives us all hope we’ll end this pandemic.”