Why is syphilis surging again? A border-city case study explains the drug shortage behind it

Syphilis was, for much of the late twentieth century, treated as a disease in retreat — a once-feared infection brought under control by decades of screening and a single, reliably effective antibiotic. That picture has changed. Case counts in the United States have risen for more than a decade, and nowhere is the resurgence more visible, or more complicated to manage, than along the border cities where Mexican and American health systems intersect. A patient case tracked by clinicians on the San Diego-Tijuana border offers a granular look at why the disease is proving so hard to beat back this time.

The frontline treatment for syphilis has not changed in generations: a long-acting injectable form of penicillin called benzathine penicillin G, sold in the US primarily under variations of the Bicillin brand name. It clears the infection reliably, crosses the placenta to protect a fetus when given to a pregnant patient, and has no real substitute for that specific use — other antibiotics can treat some stages of syphilis in non-pregnant adults, but nothing else is considered adequate to prevent congenital syphilis, the transmission of the infection from mother to baby during pregnancy.

That single point of dependency is precisely the problem. The US has experienced recurring shortages of benzathine penicillin for several years, driven by a mix of manufacturing constraints, a limited number of producers globally, and rising demand as case counts climb. When supply tightens, clinics are forced into difficult rationing decisions: prioritising pregnant patients, who face the most severe consequences from untreated infection, while delaying treatment for others or substituting less-ideal alternatives.

The patient case at the center of the reporting illustrates how these shortages play out on the ground rather than in supply-chain spreadsheets. A person diagnosed with syphilis at a border clinic faced a delay in starting the standard injectable course, not because of any diagnostic uncertainty or a change in their condition, but because the clinic's allocation of the drug had to be stretched across more patients than it was designed for. Advocates who work with patients in this position describe a recurring frustration: a treatable, curable infection that nonetheless takes weeks longer to actually treat than the science would suggest is necessary.

Congenital syphilis, in particular, has become the sharpest edge of the crisis. Cases of babies born with the infection, which can cause stillbirth, bone deformities, blindness and neurological damage, have risen sharply nationwide over the past several years — a trend public health officials describe as both preventable and, in the current supply environment, genuinely difficult to prevent. Every week that a pregnant patient's treatment is delayed by drug availability raises the risk that the infection crosses to the fetus before the antibiotic can act.

The border setting adds a further layer of complexity. Patients frequently move between health systems on both sides of the border, seeking care, work or family across San Diego and Tijuana, which means continuity of treatment depends on coordination between two different national health systems with different drug supply chains, insurance structures and reporting requirements. A shortage in one system does not necessarily mean a shortage in the other, but patients do not always have the flexibility, documentation or resources to simply seek treatment across the border when their local supply runs short.

Public health researchers studying the shortage say it reflects a broader vulnerability in how the US sources critical, low-margin generic drugs. Benzathine penicillin is inexpensive and long off-patent, which makes it commercially unattractive for manufacturers to expand production capacity even as demand rises — a pattern seen across several other cheap, essential generic drugs that have faced repeated US shortages in recent years, from certain chemotherapy agents to basic saline solutions.

Federal health agencies have taken some steps to ease the shortage, including efforts to import additional supply and to prioritise allocation toward pregnant patients and newborns at highest risk. Clinicians on the ground describe these measures as helpful but insufficient to fully close the gap between the number of diagnoses and the amount of drug available to treat them promptly, particularly in high-caseload border and urban clinics.

Researchers advocate for structural fixes rather than one-time supply injections: guaranteed manufacturing contracts that make production of the drug commercially viable long-term, stockpiling requirements similar to those used for other essential medicines, and better forecasting that ties drug procurement to the trajectory of case counts rather than reacting to shortages only after they have already disrupted patient care.

For now, the disease's return is outpacing the supply chain's ability to keep up. Syphilis is, by any clinical measure, one of the most curable infections in medicine — a single well-timed injection is usually enough. The obstacle this time is not medical uncertainty but logistics, and clinicians on the front line say that until the supply problem is fixed at its source, resurgence numbers are likely to keep climbing even as the science of how to stop them remains entirely settled.