Highlights
Researchers from UCSD have built strong relationships with communities of unhoused individuals who use drugs in San Diego and Tijuana over several years.
Since spring, about 10% of the study participants have been diagnosed with active syphilis — cases that might otherwise have gone unnoticed and untreated.
Restrictions from the NIH on foreign research partnerships have hindered the team’s ability to monitor infectious diseases, and a shortage of intramuscular penicillin further complicates complete treatment for these patients.
SAN DIEGO — She initially visited Park Boulevard for the money and snacks. A friend mentioned a place offering free snacks like fruit gummies, granola bars, and rice crispy treats — and $20 for completing some survey questions. It was a tempting offer for GB, who was used to rummaging through garbage for bottles and cans to earn money. With aluminum fetching $1.66 per pound, collecting enough to make $20 required hundreds of cans. At Park Boulevard, all she needed to do was show up. In May, she and her friend walked over from their tent city.
The location was a research office, sterile with frosted glass. As promised, there was coffee and a basket of snacks. However, she was caught off guard when the researcher interviewing her asked to draw her blood. At 47, having used meth since 2021, she was terrified of needles. She snorted her meth, never having injected or used heroin. She considered leaving but was put at ease by Carlos Vera, the researcher, who treated her with kindness and respect.
She agreed, and was shocked when Vera informed her that her initial results indicated syphilis. Her boyfriend, who had overdosed in February, was the only person she had been with for years. She had no symptoms.
Further tests were needed, but if confirmed, Vera offered to accompany her to the county clinic for treatment. He frequently encountered such cases. Although not a health professional, Vera, as an outreach coordinator for the University of California, San Diego, recruited participants for studies concerning drug use and infectious diseases in communities spanning the U.S.-Mexico border. Building trust in these communities was essential for participant recruitment. Since March, out of 81 people interviewed in San Diego, eight had active syphilis.
This was a concerning development at a time when syphilis rates, after two decades of increase, seemed to be stabilizing. However, the data was nearly two years old by the time GB was tested. Earlier in spring, the local Planned Parenthood affiliate highlighted a “silent crisis” of unreported sexually transmitted infections, mirroring the trend observed by Vera and his team. Many participants might not have been tested without the study. “I wouldn’t have known,” GB confessed.
An additional complication arose. GB resides less than 20 miles from the busiest border crossing in the Western Hemisphere. According to the Department of Homeland Security, approximately 90,000 people cross northward daily. For many, commuting between San Diego and Tijuana is routine. The study, initially intended to occur on both sides of the border, was affected when the National Institutes of Health advised that international collaboration was not a priority, and funding would be contingent on excluding the Mexican part of the proposal.
During a visit to the county clinic for syphilis treatment, Vera discovered another challenge. He expected GB to receive an intramuscular penicillin shot, which releases slowly over a week, effectively killing the bacteria. However, due to a shortage, GB was instead prescribed oral antibiotics, taken twice a day for 30 days — a regimen difficult for even those with stable housing, let alone someone living in a tent.
The risk of theft or loss of medication was high among study participants. “When police sweeps occur, they dispose of belongings, including medications,” explained Britt Skaathun, an epidemiologist at UCSD and study leader. They had seen essential medications for HIV, diabetes, and depression, as well as naloxone, disposed of this way.
Early detection of syphilis allows for a cure. However, with recruitment in Tijuana halted, some cases might be missed, and the penicillin shortage makes treatment less certain. As Vera returned from the clinic with GB, he worried whether she could complete the medication course needed for her cure.
Study as safety net
“What’s the role of an epidemiologist? Do you simply publish the data and allow others to interpret it for policy, or do you, as a researcher, bear that responsibility, knowing the data best?”
Steffanie Strathdee understood the gravity of this question. In the 1990s, while researching HIV transmission among drug users, she co-published a paper stating that needle exchanges needed to be paired with personalized services to be effective. However, a Colorado congressman misrepresented her work to argue against needle exchanges. “I was livid,” Strathdee, now a professor at UCSD, recalled. “I’m proof that without helping policymakers interpret data, it can be misinterpreted or misused.”
Strathdee and Skaathun were aware of how their work could be misused, given the focus on substance use, sexually transmitted infections, and U.S.-Mexico travel. In 2016, Donald Trump advocated for a border wall and ending drug epidemics by excluding “bad hombres.” Their research on sex, drugs, and cross-border travel could easily fuel such narratives.
The Covid-19 pandemic restrictions on travel between Tijuana and San Diego offered a natural experiment. Past studies showed infectious diseases often crossed borders. For instance, 18% of Americans with H1N1 flu in 2009 had traveled to Mexico. In 2015, Strathdee and colleagues traced HIV transmission across the border using genetic sequences. Despite travel restrictions, the study found epidemiological links remained.
Strathdee and Skaathun aimed to explore this further. In September 2023, Strathdee saw an NIH funding opportunity allowing foreign components. She confirmed that the Tijuana site could be included, emphasizing that addressing HIV among drug users in San Diego required interventions in Tijuana as well.
However, in April 2025, after receiving a promising score for their proposal, the NIH questioned the foreign component’s necessity. By May 1, 2025, the agency ceased funding proposals with foreign components pending a new grant structure, which took effect in January 2026. Without options, the UCSD team had to revise their proposal, focusing solely on San Diego.
This resulted in layoffs for eight staff members and the closure of their Mexican research office, severing ties with vulnerable communities. The study had served as a safety net, identifying cases of HIV and syphilis that might otherwise be missed. Now, the extent of missed diagnoses in Tijuana and their connection to San Diego cases remained unknown.
From a $100,000 salary to Tent City
GB was skeptical of doctors and hospitals, viewing them as businesses seeking profit. After a car accident years ago, she refused the recommended opioids and surgeries, choosing to heal on her own. More than the snacks or $20, it was the trust in the person who recommended the research office that led her to give it a chance.
They had shared an “abando,” one of the better places she had stayed. It was a three-bedroom house with a garden, occupied under an agreement with the owner’s children. They maintained the house, laid new tile, and enjoyed coffee in the garden.
When pets arrived, GB ensured they were free of fleas. “You can find a YouTube video for everything,” she said.
Her past life was dramatically different. Married for 23 years with a career in military contracting, she earned $100,000 and had kids with braces. Her son loved “Beverly Hills Chihuahua,” so she got him a similar dog. Things started unraveling in 2020. Covid hit, and her sister, close to her, died by suicide. They had spoken daily.
GB began using drugs, eventually addicted. She drifted around the city, staying in a broken-down RV left by a friend, which was eventually towed due to tickets. She stayed at the “abando” until it became too risky. “A friend advised leaving due to a sex worker’s traffic,” she explained. She later lived in a tent with her boyfriend, who was addicted to fentanyl. Initially addicted to heroin, he became involved in gangs and was in and out of jail, but he was sweet. For her birthday, he brought ice cream and cake from the food bank and organized a picnic on the library’s rooftop terrace. She attended all his court dates.
After he was gone, GB, once cautious of official homelessness programs, sought help. She knew someone who had found stable housing through municipal tent city programs. She sought that stability, called the number, and was picked up, moving into a tent in the shadow of I-5.
The stigma of syphilis was overwhelming, more so than addiction or homelessness. People talked about drug use and camping locations, but not about syphilis. She didn’t want anyone to know she was diagnosed, agreeing to be interviewed using only her initials.
She liked the clinic Vera took her to. The doctor treated her well, explaining that her facial rash was not syphilis-related but due to harsh living conditions and provided her with cream. Without testing, she might not have known about the infection, which could remain unnoticed for years. It could cause a painless mark, increase vulnerability to HIV, and cause a faint rash or flu-like symptoms. GB’s fatigue was not unusual.
GB, compared to many participants, was well-positioned to manage twice-daily pills. She had stable sleeping arrangements and wasn’t at risk of receiving eviction notices. She described herself as “an uppity homeless.” While her speech was rapid due to meth, her addiction wasn’t severe. She was functional, maintaining hygiene and avoiding expired food. She was motivated to clear the infection, keeping her pills in a purse she always had. Despite this, researchers worried. Sometimes, after late nights recycling, she lost track of days. Vera occasionally had to search the tents to find her for meetings.
‘How many people did you revive in the last two weeks?’
“Do you need Narcan?” Vera asked a man in a black T-shirt.
“Yeah!” he answered, appearing older than his 32 years, his back bent under an unseen burden.
Vera was near 17th Street, where he had previously revived someone using naloxone. The tents lining the sidewalk began to stir as the morning fog lifted. Recognizing Vera’s rapport with the community, a local program provided him with naloxone to distribute. He was ensuring people had enough to save lives if needed, also using the opportunity to check in with study participants and recruit new ones.
Each tent bore a neon yellow notice. “24 Hour Notice of Cleanup and Property Removal,” it warned, referencing the San Diego Municipal Code violations.
“Do you need Narcan?” Vera asked again.
A woman emerged, squinting. “How many can you give me?” Vera handed her ten boxes, one by one, until her arms were full.
“How many people did you revive in the last two weeks?”
“One. No, two.”
“How many Narcans did you use?”
“Seven.”
“Wow, that’s a lot.”
Vera then leaned into a makeshift shelter and recognized a study participant. “Hey, Christina! How are you? Do you need Narcan?” He greeted her dog, Buttercup, with a scratch behind the ears.
Christina had matters to discuss with Vera: samples to hand over and a wound needing attention. He took her to the van for privacy and found alcohol swabs to clean her ankle. Although not on the NIH-funded clock, Vera’s interactions, like knowing Christina and her situation, were crucial. Such daily interactions, now lost in Tijuana, were integral to the study.
Despite changes in federal funding, this work required time. The rapport Vera built, person by person, led to vital data and diagnoses. Population-level numbers masked the individuals and the close relationship between research and practice.
The penicillin shortage highlighted public health’s fragility. Demand often exceeded supply due to rising syphilis rates and reduced sexual caution with improved HIV treatments. Additionally, manufacturing vulnerabilities existed, with only one U.S. factory producing prefilled syringes. A 2025 recall exacerbated the issue.
This led to rationing recommendations, prioritizing pregnant patients to prevent congenital syphilis. In theory, others like GB could use doxycycline pills, but adherence was challenging due to side effects and daily dosing requirements.
Vera worried about participants with severe substance use disorders, who struggled with daily life. “She’s not using often,” he noted about GB, as he drove to check on people sleeping in RVs. “Heavy users cannot function at all.” Bringing them to a free clinic in a lucid moment felt like a stroke of luck. In such cases, every dose was critical.
The federal government explored solutions for the penicillin shortage, such as testing expired syringes, importing similar European drugs, and funding public health departments to purchase imported drugs.
While some government-funded syphilis research continued, NIH-related issues were delaying potential solutions to the shortage. Preliminary evidence suggested some patients might only need one injection instead of three, which could expand supply. However, robust data was necessary to change guidelines. In June 2025, Jeffrey Klausner from USC submitted an NIH application for a clinical trial to address this, expecting a three to four-year project. Despite a favorable review, a year later, he awaited an official response.
On June 11, a grants management specialist explained, “Currently there are an overwhelming number of grants that are due and overdue for processing.” Similar delays were reported by other researchers, following NIH mass layoffs in 2025. By July 1, 2026, Klausner was informed of funding, but the award notice was delayed. The NIH declined to comment on specific grant deliberations.
Federal funding complexities may seem distant to those living under a San Diego highway, yet medication availability hinged on evidence accumulated one grant at a time. Diagnoses might depend on a friend’s tip about a nearby research office offering $20 and snacks.
‘Something to drink, something to eat?’
Returning to the office after distributing naloxone, Vera found three men waiting. One paced nervously, another leaned on a liquor store’s sign advertising vodka. They had tried the office door, but it was locked during lunch.
Vera’s phone rang as he parked the van.
“UCSD, this is Carlos. How can I help you? Yes, sir, I remember you. I see you right now. I’m across the street.”
He entered the office first, then unlocked the door. The nervous man entered, wearing a Dodgers jersey and a green bandana tied like a crest.
“Hello, sir,” he greeted.
“How’s it going?” Vera responded.
“I just wanted to let you know I was here, and to thank you for everything.”
“No worries. I appreciate you.”
The man sat. Already enrolled, he had attracted the interest of the other two men, who were also present. One, with a tattoo over his eyebrow, a yellow ballcap, and a stained hoodie, entered next.
“You can come in and sit down, we’re going to help you in a little bit, OK?” Vera said. “You want something to drink, something to eat?”
“Sure, to eat.”
“We can make a cup of noodles. We have coffee, we have chocolate, we have candy.”
“That sounds good.”
STAT’s coverage of health inequities is supported by a grant from the Commonwealth Fund. Our financial supporters are not involved in any decisions about our journalism.
