BACKGROUNDCongenital syphilis is a potentially serious, but preventable infection. Several European countries have recently reported increasing trends.AIMThis study assessed national incidence and temporal trends of congenital syphilis and prevalence of pregnancies with active syphilis in Denmark between 2010 and 2024.METHODSUsing nationwide individual-level data linked through civil registration numbers across Danish health and population registers, we identified all maternal and congenital syphilis cases among live-born children born in Denmark from 2010 to 2024. We calculated annual incidence per 10,000 live births and analysed temporal trends and annual percent change (APC) with 95% confidence intervals (CI), using Poisson or negative binomial regression models.RESULTSFive infants with confirmed congenital syphilis were recorded among 894,345 live births, corresponding to an incidence of 0.6 per 100,000 (95% CI: 0.2-1.4). No infants with congenital syphilis were identified after 2016. For each infant, a plausible explanation for screening failure was identified: two women arrived in Denmark late in pregnancy, two were infected late in pregnancy. None of these events reflected failure of the first-trimester screening algorithm itself. One event was due to a reporting irregularity. Poisson regression showed a decreasing trend (APC = -21.7%; 95% CI: -43.4 to -1.0). Active syphilis infection occurred in 172 pregnancies, amounting to 20.0 per 100,000 live births (95% CI: 17.2-23.2) with no temporal changes.CONCLUSIONSCongenital syphilis is now eliminated in Denmark. The incidence of pregnancies with active syphilis infection remained stable despite increasing syphilis prevalence in the general population, confirming the continued effectiveness of the Danish national antenatal syphilis screening programme.

Vertical transmission of sexually transmitted infections remains a public health concern, particularly in socially vulnerable settings. Although Brazil has achieved the elimination of mother-to-child transmission of HIV, syphilis during pregnancy continues to pose significant challenges, especially in the northern region. This cross-sectional study aimed to estimate the prevalence of HIV and syphilis and identify associated factors among pregnant women receiving prenatal care in Belém, Pará, Brazil. Between April and June 2021, 398 pregnant women were interviewed using a structured clinical-epidemiological questionnaire and underwent laboratory testing. HIV diagnosis was established using fourth-generation serological assays with immunoblot confirmation, and syphilis diagnosis was based on nontreponemal testing followed by treponemal confirmation. Descriptive analyses were performed, followed by bivariate analyses using Fisher's exact test, chi-square test with Monte Carlo simulation, and Mann-Whitney U test, and Poisson regression with robust variance was applied to estimate prevalence ratios for syphilis. The prevalence of syphilis was 6.36%, and HIV prevalence was 1.01%. Psychoactive substance use was the only variable independently associated with syphilis positivity, while other sociodemographic and behavioral factors showed descriptive trends without statistical significance, and no significant associations were observed for HIV infection. These findings indicate that persistent social and behavioral vulnerabilities, particularly psychoactive substance use, contribute to ongoing syphilis transmission during pregnancy, underscoring the importance of integrating substance use screening, targeted counseling, and harm-reduction strategies into prenatal care to advance efforts toward eliminating vertical transmission of sexually transmitted infections.

Objectives. To assess trends in prenatal syphilis screening and treatment in the United States and evaluate newborn syphilis screening. Methods. We conducted a retrospective cohort study using Medicaid (2014-2021) and commercial insurance claims (2010-2023). We assessed syphilis screening by trimester, repeat screening (> 1 trimester), temporal trends, treatment with benzathine penicillin G or nonrecommended antibiotics, and screening of infants born to pregnancies diagnosed with syphilis within 30 days of birth. Results. Syphilis screening occurred in 75.2% of Medicaid-insured and 92.8% of commercially insured pregnancies; 51.8% and 81.7%, respectively, were screened in the first trimester. Screening increased in Medicaid (67.6% to 80.5%) and remained high in the commercially insured cohort (91.0% to 94.0%). Repeat screening more than doubled in both cohorts. Approximately half of pregnancies diagnosed with syphilis had evidence of benzathine penicillin G treatment, whereas 5% to 6% had evidence of nonrecommended antibiotics. Infant screening was rarely identified, likely reflecting incomplete capture in claims data. Conclusions. Prenatal syphilis screening in the United States may fall short of recommendations, although increasing repeat screening is encouraging progress. (Am J Public Health. Published online ahead of print September 3, 2026:e1-e10. https://doi.org/10.2105/AJPH.2026.308657).

This retrospective single-center study compared nucleic acid testing (NAT), time-resolved fluorescence immunoassay (TRFIA), and enzyme-linked immunosorbent assay (ELISA) for screening hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency virus (HIV), and Treponema pallidum (TP) among 1243 preoperative and pre-transfusion patients. Specimens were detected by pathogen-targeted NAT, serological TRFIA and routine ELISA panels, respectively. HBV positive rates were 2.17% (NAT), 2.09% (TRFIA) and 1.53% (ELISA); HCV positive rates were 0.08%, 0.24% and 0.08%, without statistical intergroup differences (all p > 0.05). TRFIA yielded a significantly higher TP positive rate than ELISA (0.88% versus 0.40%, p < 0.05), while no HIV-positive specimens were identified in this cohort. Kappa tests showed moderate-to-good consistency for HBV (0.711-0.842) and perfect concordance between NAT and ELISA for HCV (Kappa = 1.000). Twenty-three discordant samples were found, including eight NAT-only HBV positives suggestive of potential window-period infections and six TRFIA-only TP positives. Limited by an obstetric-female-dominated cohort, scarce HCV cases, and zero HIV positives, standard diagnostic accuracy metrics could not be comprehensively evaluated. NAT and TRFIA exhibit complementary screening values, yet their combined application may increase false-positive risks and lacks systematic cost-effectiveness evidence to support large-scale clinical implementation.

Background. Histological examination and rabbit intratesticular inoculation of clinical specimens are traditionally used to diagnose syphilis and characterize the aetiological agent, Treponema pallidum. Usually, these methods provide only qualitative data of the bacterium. For quantitative analysis, dark-field microscopy and real-time PCR are commonly used but both methods have important limitations. We investigated intradermal inoculations in rabbits as a sensitive and quantitative alternative test method.Methods. We prepared 10-fold serial dilutions of a treponemal stock ranging from 4×10[3] to 4 treponemes ml[-1]. Each dilution series was injected intradermally in two rabbits, ten sites per rabbit. Similarly, each dilution was inoculated intratesticularly into two rabbits, four dilutions in a total of eight rabbits. We scored and measured the size of lesions at the injection sites in rabbits inoculated intradermally. We monitored intratesticularly infected rabbits for orchitis. Sera from all animals were tested for seroconversion. We also compared the analytical sensitivity of animal bioassays to that of treponemal PCR.Results. The infectivity titre of T. pallidum was the same whether measured by intradermal or intratesticular inoculations, but the former used 75% fewer animals. Bacterial concentration at 50% endpoint was lower, 4 treponemes ml[-1], with intratesticular route compared to 25 treponemes ml[-1] using intradermal injections. Nested PCR demonstrated an analytical sensitivity of 40 treponemes ml[-1], comparable to that obtained with animal bioassays. We also showed a correlation between lesion size and treponemal counts that, under standardized conditions, might be exploited to estimate the number of treponemes in a sample.Conclusions. Our studies showed that all methods tested detected T. pallidum with similar sensitivities. However, the intradermal route might be better suited to investigate clinical specimens as it offered desirable features such as treponemal quantification, minimal number of animals required and detection of live infectious bacteria, all in a single test.

The Syphilis Point of care Rapid testing and Immediate Treatment Evaluation (SPRITE) is a collaborative, community-based initiative that strengthens syphilis prevention and control in Ontario, Canada through flexible outreach nursing and point-of-care testing (POCT) and immediate treatment. Seven public health units (PHUs) partnered with 86 community-based organizations (CBOs) to deliver syphilis/HIV POCTs in underserved settings. This study evaluated a real-time knowledge exchange network that supported syphilis POCT implementation and capacity-building across PHUs and CBOs in Ontario.

Treponema pallidum subsp. pallidum is the causative agent of syphilis, a chronic and potentially devastating infection that is resurging globally. The bacterium is highly invasive, disseminates rapidly, and establishes decades-long latency that may progress to severe tissue destruction and death. T. pallidum's reduced genome contributes to its dependence on the host. Its impressive TprK antigenic variation, scarce outer membrane proteins, and periplasmic flagella provide for immune evasion, enabling persistence and reinfection. Our understanding of syphilis pathogenesis derives largely from experimental infection in rabbits and from historical studies in humans, though recent advances in continuous cultivation, genetic manipulation, hybrid-capture genome sequencing, and multi-omic approaches have opened new avenues for dissecting host-pathogen interactions and disease pathogenesis. This review highlights mechanisms of syphilis pathogenesis, the central role of the immune response in disease causation and progression, and the role of new technologies in answering long-standing questions and informing vaccine development.