Health Econ
HAART’s success may have fueled syphilis resurgence
Clinical takeaway: Transformative HIV treatments can change sexual risk dynamics at the population level; clinicians should pair advances like HAART with ongoing STI prevention, screening, and counseling—especially for higher‑risk groups.
Syphilis was nearing elimination in the United States by 2000, but incidence has since rebounded sharply, reaching a 60‑year high. A new analysis suggests that the introduction of highly active antiretroviral therapy (HAART)—which dramatically reduced HIV mortality—may have contributed to this reversal through unintended consequences.
Using national CDC data from 1991 to 2008, researchers examined whether syphilis rates rose more in states with higher pre‑HAART AIDS prevalence, where HAART uptake and survival benefits were greatest. Employing a triple‑difference analytic approach (by state, sex, and time), they found that a one standard‑deviation increase in pre‑HAART AIDS prevalence was associated with a 17.8% increase in syphilis incidence after HAART was introduced. The rise was largely concentrated among men, consistent with higher HIV prevalence and HAART use in this group.
The researchers estimate that, in the absence of HAART, there would have been 81% fewer syphilis cases—about 71,000 diagnoses—between 1996 and 2008. The rise was driven not only by increased longevity among people living with HIV but also by shifts in sexual behavior following reduced HIV mortality and perceived transmission risk.
While emphasizing that HAART’s benefits overwhelmingly outweigh these effects, the analysis underscores the importance of anticipating behavioral responses to medical breakthroughs. The authors suggest that pairing life‑saving HIV therapies with enhanced STI prevention efforts—such as more frequent syphilis screening, targeted counseling, and expanded public health services—may help mitigate unintended downstream impacts.
Source: Beheshti, D, et al. 2026. Health Econ. Unintended Consequences of Life-Saving Pharmaceutical Innovations: How HAART Led to the Resurgence of Syphilis