The joinpoint analysis identifying four distinct phases adds interpretive value beyond what a simple linear trend could convey. The rapid growth phase from 2005 to 2008, with an annual percentage change of 25.23 percent, likely reflects a combination of genuine transmission intensity and expanding case-finding capacity. The China Information System for Disease Control and Prevention, launched nationally after the 2003 SARS epidemic, mandated that hospitals, community health centers, and township facilities report confirmed syphilis cases within 24 hours of diagnosis. As this real-time reporting infrastructure matured in the mid-2000s, previously uncounted cases would have entered the system, inflating apparent incidence even before any true change in transmission. Disentangling ascertainment effects from genuine epidemiological shifts is a perennial challenge in interpreting notifiable disease data, and the authors’ reliance on a single passive surveillance source means some caution is warranted when attributing every inflection point to changes in disease dynamics alone.

The mild decline phase from 2008 to 2019, with an annual percentage change of negative 5.00 percent, coincides with a period in which China scaled up syphilis screening in antenatal clinics, expanded free treatment policies, and integrated sexually transmitted infection services into broader HIV prevention frameworks. The accelerated decline from 2019 to 2023, at negative 18.69 percent annually, and the apparent reduction phase from 2023 to 2025, at negative 39.01 percent annually, are striking in their steepness. Part of this acceleration plausibly reflects genuine programmatic success, including expanded provider-initiated testing and partner services. However, the timing also overlaps with the COVID-19 pandemic and its aftermath, during which healthcare-seeking behavior, screening volumes, and reporting practices were disrupted across China and globally. Reduced opportunistic screening during lockdown periods and altered healthcare utilization patterns could suppress reported incidence independently of true transmission declines. The authors acknowledge residual challenges such as hidden undiagnosed latent infections, and the extraordinarily steep final-phase decline should be read with this measurement context in mind.

The dominance of latent syphilis across all stages and throughout the entire study period deserves particular emphasis. Latent syphilis is defined by the absence of clinical symptoms despite serological evidence of infection, and it is detected almost exclusively through screening rather than symptomatic presentation. A high proportion of latent cases in surveillance data can indicate two very different realities: either widespread successful case-finding that captures asymptomatic infections before they progress, or a large reservoir of undiagnosed infection circulating silently in the population. Because latent syphilis can still be transmitted vertically from mother to fetus and can reactivate or progress to tertiary disease, the persistent latent predominance in Xihu District suggests that screening intensity, not just symptomatic care, drove much of the observed epidemiology. The steep decline in primary and secondary syphilis, with average annual percentage changes of negative 14.76 percent and negative 12.19 percent respectively, is more directly interpretable as a reduction in recently acquired infections, since these stages manifest with characteristic lesions that prompt clinical presentation.

The near-disappearance of congenital syphilis is among the most consequential findings for public health practice. The surge in congenital cases during 2006 and 2007 aligns with the tail end of the national epidemic’s growth phase, when maternal infection prevalence was high and routine antenatal syphilis screening was not yet universal. China subsequently made antenatal syphilis testing a standard component of prenatal care and, in 2010s policy iterations, provided free screening and treatment for pregnant women. The fact that no notified congenital syphilis cases have been recorded in Xihu District since 2017 represents achievement of a milestone that the World Health Organization’s global strategy frames as central to elimination efforts. The WHO targets for 2030 include reducing adult syphilis incidence by 90 percent relative to a 2020 baseline and keeping congenital syphilis below 50 cases per 100,000 live births. Xihu District’s congenital notification rate of zero for eight consecutive years exceeds that threshold by a wide margin, though maintaining elimination requires sustained vigilance, since congenital syphilis can re-emerge quickly if antenatal screening coverage lapses.

The gender disparity in decline rates, with females showing an average annual percentage change of negative 10.23 percent compared with negative 5.54 percent among males, is consistent with patterns observed in many syphilis control programs. Women are more likely to encounter the healthcare system through reproductive health services, antenatal visits, and gynecological care, creating additional screening touchpoints that men typically lack. This structural asymmetry in healthcare contact means that male-focused outreach, including services delivered through venues frequented by men who have sex with men, migrant worker populations, and other groups with limited routine care engagement, remains essential for closing the gap. The faster decline among women also compounds the significance of the congenital syphilis elimination, since reduced maternal infection directly protects pregnancies.

The age-stratified findings highlight two populations requiring continued attention. Adults aged 20 to 39 consistently carried the highest reported incidence burden, with a long-term average annual percentage change of negative 10.47 percent. This age concentration reflects peak sexual activity years and aligns with national Chinese data showing syphilis incidence rising among adolescents and young adults even as overall trends improved. Interventions tailored to this group, including digital outreach, youth-friendly clinic services, and integration with HIV pre-exposure prophylaxis programs, are logical priorities. The elderly population aged 60 and above presented a different pattern: prominent high reported incidence before 2019 followed by a sharp drop, with an average annual percentage change of negative 9.53 percent. Elevated syphilis rates among older adults in China have been attributed in part to widespread opportunistic screening during hospital admissions and health examinations, which can detect long-standing latent infections, as well as to genuine transmission within this age group. The post-2019 decline among the elderly may partly reflect changes in screening practices during the pandemic era, again underscoring the need to distinguish reported incidence from true incidence.

Tertiary syphilis remained at extremely low absolute levels with sparse case counts throughout the 21 years, which is expected given that tertiary disease develops years to decades after initial infection and requires prolonged untreated latency. The rarity of tertiary cases in the surveillance record suggests either effective interruption of progression through earlier detection or under-ascertainment of late manifestations that present to cardiology, neurology, or ophthalmology services without syphilis serology being ordered. Sparse counts also limit statistical power for trend estimation in this subgroup, a limitation inherent to analyzing rare outcomes.

Several methodological considerations frame the interpretation of these findings. The study uses reported rather than confirmed incidence, meaning case counts depend on diagnostic criteria, testing frequency, and reporting compliance, all of which changed over the study window. Diagnostic classification shifted from the GB 15974-1995 standard to WS 273-2007 in 2007 and then to WS 273-2018 in 2018, and such criteria revisions can introduce artificial discontinuities in staged case counts. Population denominators drawn from municipal statistical bureau estimates may not fully capture the massive migrant population flowing through Xihu District, potentially distorting rate calculations in either direction. Joinpoint regression, while powerful for identifying inflection points, can be sensitive to the number of allowed joinpoints and to short-term fluctuations, particularly in the final 2023 to 2025 segment where only a few data points drive the steep negative 39.01 percent estimate.

Despite these caveats, the overall picture is one of substantial, sustained progress. A decline from a peak of 155.16 per 100,000 to 13.17 per 100,000 over fifteen years represents roughly a 92 percent reduction from the epidemic’s height, approaching the scale of reduction the WHO envisions globally by 2030. For a district once classified as hyperendemic, this trajectory demonstrates that comprehensive, long-duration control programs combining surveillance, universal antenatal screening, accessible treatment, and targeted outreach can fundamentally reshape local syphilis epidemiology. The residual challenges the authors identify—persistent vulnerability among young adults and the elderly, and the hidden burden of undiagnosed latent infection—define the agenda for the next phase of control, in which the final mile toward elimination will likely prove more demanding than the steep initial decline. Lessons from Xihu District are relevant beyond Zhejiang, offering a template for other high-burden urban districts navigating the transition from epidemic containment to elimination-level targets.

Subject of Research: Epidemiological trends of reported syphilis incidence in Xihu district, Hangzhou, China, 2005–2025

Article Title: Epidemiological trends of reported syphilis incidence in Xihu district, Hangzhou, China, 2005–2025

Article References: Li, J., He, L., Wu, T., Meng, J., Wang, T., Sun, F., & Wang, B. (2026). Epidemiological trends of reported syphilis incidence in Xihu district, Hangzhou, China, 2005–2025. Frontiers in Epidemiology, 6, Article 1944790. https://doi.org/10.3389/fepid.2026.1944790

Image Credits: AI Generated

DOI: 10.3389/fepid.2026.1944790

Keywords: Epidemiological, trends, reported, syphilis, incidence, Xihu, district, Hangzhou, China, scientific research

Researchers led by Zheng Yang of the Emergency Department at Tongde Hospital of Zhejiang Province, affiliated with Zhejiang Chinese Medical University, analyzed 3,327 exposure-related clinic presentations recorded between October 2022 and October 2025. The team began with a larger pool of records and applied rigorous exclusion criteria, removing seven system-test entries, fifteen exposures classified as World Health Organization Category I, thirteen confirmed continuation visits, ten records with contradictory dates, and two unresolved duplicates. What remained was a clean hospital-based cohort suitable for examining two distinct questions: how quickly patients presented after a potential rabies exposure, and whether they had attempted any wound care on their own before arriving at the clinic.

The central finding concerns timing. Of the 3,327 presentations, 218, or 6.6 percent, occurred on a calendar day after the day of injury. Because the study relied on electronic medical records rather than precise timestamps, the researchers used a date-based operational proxy for delay: presenting on a subsequent calendar day rather than the same day. This is a conservative measure, and the authors are careful to frame it as such, but it captures a meaningful gap in access to care. Rabies virus travels along peripheral nerves at a relatively slow rate, and every hour of delay before prophylaxis begins extends the window during which the virus could, in principle, establish itself at the wound site and begin its ascent.

When the researchers fitted multivariable logistic regression models adjusting for other characteristics, patients aged 65 and older had significantly higher adjusted odds of subsequent-calendar-day presentation compared with the reference group aged 15 to 44 years. The adjusted odds ratio was 2.28, with a 95 percent confidence interval of 1.31 to 3.96 and a P value of 0.003. In practical terms, older adults in this cohort were more than twice as likely to show up at the clinic only after the calendar day of their exposure had passed. This age-related pattern persisted even after accounting for other variables in the model, suggesting that advancing age itself, or factors closely tied to it, creates a genuine barrier to prompt care-seeking after an animal bite or scratch.

The study also examined pre-hospital wound management, the self-directed cleaning or treatment that patients perform before reaching professional care. Guidelines from the World Health Organization emphasize immediate and thorough washing of bite wounds with soap and running water for at least fifteen minutes, a simple intervention that mechanically reduces viral load at the exposure site. The researchers modeled any pre-hospital wound self-treatment as a separate binary outcome. Interestingly, the estimate for the oldest age group pointed in the opposite direction: patients aged 65 and older appeared less likely to report any self-treatment, with an adjusted odds ratio of 0.71 and a confidence interval of 0.50 to 1.01. However, this estimate did not reach the conventional threshold of statistical significance, with a P value of 0.056, and the authors explicitly caution that it is imprecise and requires confirmation in future work.

A methodologically important point in the paper is that the two outcomes were modeled separately. The authors stress that their analysis does not establish a combined individual-level outcome linking delay and self-treatment within the same patient. In other words, the data cannot tell us whether an older adult who delays presentation is also the same person who skips wound washing, or whether these behaviors occur independently across the cohort. This distinction matters for intervention design: if delay and inadequate wound care cluster in the same individuals, targeted outreach could address both at once, whereas independent patterns might require broader, population-level messaging.

Two other associations emerged from the models. Patients who reported any pre-hospital wound self-treatment had higher adjusted odds of subsequent-calendar-day presentation, with an adjusted odds ratio of 2.72 and a 95 percent confidence interval of 2.00 to 3.69. One plausible interpretation is that people who attempt self-care may believe they have managed the problem adequately and therefore postpone professional evaluation, though the observational design of the study prevents any firm causal claim. The temporal pattern of the data also revealed that presentations during the clinic-opening calendar period of October through December 2022 were associated with subsequent-calendar-day presentation, with an adjusted odds ratio of 2.54. The authors interpret this finding as exploratory, noting that it may reflect the establishment phase of the clinic itself, shifts in case mix, seasonality of animal exposures, or unmeasured access factors rather than any stable behavioral pattern.

The implications for rabies control programs, particularly in China where dog-mediated rabies persists at low but nonzero levels, are significant. Older adults represent a vulnerable population on multiple fronts. They may have reduced mobility, limited awareness of modern PEP protocols, greater reliance on traditional remedies, or fewer social contacts who can urge them to seek care quickly. Sensory and cognitive changes can also affect how seriously a minor bite wound is perceived. Because the incubation period of rabies can range from weeks to months depending on the site and severity of exposure, a delay of even one day is unlikely to be decisive in every case, but the cumulative effect of late presentation across a population contributes to preventable deaths. Public health campaigns that specifically target older adults, perhaps through community health workers, primary care touchpoints, or family-centered messaging, could help close this gap.

The study’s design has limitations that the authors acknowledge. As a retrospective, single-center, hospital-based analysis, it captures only people who eventually reached the clinic, leaving unexamined the experiences of exposed individuals who never sought care at all. The date-based proxy for delay is coarser than exact time-to-presentation measurements, and self-reported wound treatment is subject to recall bias. The clinic-opening period association is explicitly flagged as potentially confounded by factors the data cannot disentangle. Nevertheless, the large cohort size, careful data cleaning, and transparent statistical reporting give the findings credibility, and the consistency of the age effect with prior studies cited in the paper’s supplementary comparisons, including work from Hangzhou and Wuhan, strengthens the case that delayed presentation among older adults is a reproducible phenomenon rather than a local artifact.

Funded by the Zhejiang Provincial Bureau of Disease Control and Prevention Science and Technology Program, the study received ethics approval from Tongde Hospital of Zhejiang Province and was conducted on de-identified electronic medical record data with a waiver of informed consent, in accordance with the 2013 Declaration of Helsinki. As rabies continues to kill an estimated tens of thousands of people worldwide each year, most of them in Asia and Africa, research of this kind translates a grim global statistic into actionable local insight. The message for clinicians and health communicators is clear: when it comes to rabies post-exposure prophylaxis, age is not just a demographic variable but a risk factor for the behaviors that allow a preventable disease to claim lives. Ensuring that older adults recognize exposures as emergencies, wash wounds immediately, and reach prophylaxis clinics without delay may prove one of the most cost-effective interventions available in the ongoing effort to eliminate rabies deaths.

Subject of Research: Age-related delays in seeking rabies post-exposure prophylaxis and pre-hospital wound care after animal exposures

Article Title: Age-related patterns in delayed presentation and pre-hospital wound management for rabies post-exposure prophylaxis: a retrospective hospital-based study in Hangzhou, China, 2022–2025

Article References: Yang, Z., Zhu, Y., Cao, K., Yi, X., Tian, S., Yan, B., & Zhao, Z. (2026). Age-related patterns in delayed presentation and pre-hospital wound management for rabies post-exposure prophylaxis: a retrospective hospital-based study in Hangzhou, China, 2022–2025. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14571-1

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14571-1

Keywords: rabies, post-exposure prophylaxis, older adults, wound management, delayed presentation, China, Hangzhou, retrospective study, public health, geriatrics, animal bites, BMC Infectious Diseases

Circulating recombinant forms, or CRFs, arise when two different HIV-1 subtypes recombine within a coinfected host, producing a mosaic genome that can then propagate through a population. CRF67_01B is one such mosaic, and its emergence illustrates a recurring problem in HIV control: once a recombinant strain establishes a foothold, its subsequent spread can escape the attention of surveillance systems that operate within provincial boundaries. Because each region sequences and reports viral genomes largely in isolation, the true geography of transmission can remain hidden until someone stitches the fragments back together. That is precisely what the Hangzhou team set out to do, drawing on viral genetic data that carry within them a record of who infected whom, when lineages diverged, and how the virus moved across the map.

The study assembled 183 CRF67_01B pol gene sequences sampled between 2011 and 2024 across six provinces. The researchers combined sequences generated locally in Hangzhou with publicly available sequences retrieved from the Los Alamos National Laboratory HIV Sequence Database, one of the largest repositories of HIV genetic data in the world. The pol gene, which encodes the virus’s essential enzymes and is routinely sequenced for drug-resistance testing, serves as a convenient and information-rich marker for molecular epidemiology. By comparing these sequences, the team could identify viruses that were so genetically similar that their carriers were likely connected directly or through a short chain of intermediate infections.

To construct those connections, the researchers built a distance-based molecular network, a technique in which each viral sequence becomes a node and pairs of sequences separated by fewer genetic differences than a chosen threshold are joined by edges. At a genetic distance threshold of 0.6 percent, the network resolved the 183 sequences into 24 putative transmission clusters, and 99 of the 183 sequences, an entry rate of 54.1 percent, fell into one of those clusters. That is a striking figure: it means that more than half of the people carrying this strain in the dataset are genetically linked to at least one other person in the network, indicating active and recent chains of transmission rather than scattered, independent introductions. The demographic pattern within those clusters was even more pronounced. Men who have sex with men accounted for 91.9 percent of the clustered individuals, confirming that this recombinant form has become firmly embedded in that community across the sampled provinces.

When the researchers examined the links that crossed provincial boundaries, one pairing stood out above all others: connections between Jiangsu Province and Hangzhou dominated the interprovincial portion of the network. This observation immediately suggested a direction of flow, with the virus moving from an established epidemic center in Jiangsu into the Zhejiang provincial capital and beyond. But a molecular network alone can only show that two viruses are related; it cannot say which lineage came first or reconstruct the historical routes the virus took. For that, the team turned to Bayesian phylogeography, a family of statistical methods that treats the geographic locations of viral ancestors as unknown variables to be inferred from the tree of genetic relationships.

The phylogeographic analysis, combined with a technique known as Bayesian stochastic search variable selection, or BSSVS, allowed the researchers to test which migration pathways between provinces were supported by the data rather than merely plausible. BSSVS works by allowing the model to switch migration rates on and off across the phylogenetic tree and retaining only the connections that measurably improve the explanation of the observed sampling locations. From this inference, the team estimated the time to the most recent common ancestor of the sampled CRF67_01B sequences, arriving at an origin in Jiangsu Province around 2007, roughly six years before the strain was first formally identified in China. The lag between true emergence and first detection is a familiar lesson of viral genomics, and it underscores how much transmission can occur before a novel recombinant attracts scientific attention.

The reconstruction also captured the epidemic’s tempo. After its origin around 2007, CRF67_01B entered a phase of exponential growth between 2009 and 2011, the classic signature of a lineage exploiting an under-saturated network of susceptible hosts. Growth then slowed, declined between 2017 and 2020, and subsequently leveled off into a plateau. That plateau does not mean the strain has been contained; rather, it suggests that the epidemic has reached a kind of equilibrium within its host population, with ongoing transmission balanced by the natural depletion of uninfected contacts, treatment-driven reductions in infectiousness, and behavioral changes. The inferred migration pathways tell a complementary story of movement: from Jiangsu into Hangzhou, from Hangzhou onward into Anhui, and from Jiangsu, Hangzhou, Anhui, and Ningbo converging into Guangdong, a province whose economic gravity draws large numbers of internal migrants.

Technically, the study demonstrates the value of combining two complementary molecular epidemiological tools. Distance-based networks are computationally inexpensive, transparent, and well suited to identifying recent transmission pairs and clusters, but they are blind to direction and time. Bayesian phylogeography is far more computationally demanding and depends on modeling assumptions, yet it recovers the temporal depth and directional flow that networks cannot. Used together, the two approaches allowed the authors to show not only that CRF67_01B sequences from Hangzhou cluster with those from Jiangsu, but that the common ancestor of the whole lineage most likely lived in Jiangsu around 2007 and that the branching order of migrations follows a coherent historical narrative matching the growth phases visible in the skyline plot of effective population size.

The public health implications are clear. An emerging recombinant strain circulating across provincial lines within a highly connected sexual network cannot be controlled by any single jurisdiction acting alone. The authors argue that their findings call for cross-regional joint prevention and control strategies, with interventions targeted at hub cities that serve as sources and conduits of viral spread, and at the high-risk MSM populations in which the strain is concentrated. In practical terms, this means coordinated partner notification across provincial boundaries, harmonized surveillance that shares sequence data in near real time, and prevention services, including testing, pre-exposure prophylaxis, and rapid treatment initiation, concentrated in the urban nodes the phylogeography identifies as transmission hubs. Hangzhou’s epidemic, on this reading, is best understood as epidemiologically linked to surrounding and earlier epicenters, and any strategy that treats it as a local problem will miss the upstream reservoirs that continually seed new infections.

The research also highlights the necessity of open genetic data. A substantial fraction of the sequences in this analysis came from a public database rather than from the authors’ own laboratory, and the cross-provincial picture would have been impossible without that shared resource. As HIV-1 continues to generate new recombinant forms worldwide, the combination of open sequence repositories, molecular network analysis, and Bayesian phylodynamic inference offers health authorities a way to see epidemics as they truly are: continuous, connected, and indifferent to administrative borders. For CRF67_01B, the genetic record now shows a lineage born in Jiangsu around 2007, exploding within the MSM community early in the following decade, and weaving an enduring web of transmission from the Yangtze delta to the south of China. The task that remains is to translate that molecular cartography into prevention that moves as fast and as far as the virus does.

Subject of Research: Spatiotemporal dynamics and cross-regional transmission of HIV-1 CRF67_01B in China

Article Title: Spatiotemporal dynamics and cross-regional transmission network of HIV-1 CRF67_01B in six provinces in China

Article References: Ye, L., Xu, K., Luo, W., Wu, S., Zhu, M., Zhang, X., & Sun, Z. (2026). Spatiotemporal dynamics and cross-regional transmission network of HIV-1 CRF67_01B in six provinces in China. Virology Journal. https://doi.org/10.1186/s12985-026-03302-2

Image Credits: AI Generated

DOI: 10.1186/s12985-026-03302-2

Keywords: HIV-1, CRF67_01B, circulating recombinant form, molecular transmission network, Bayesian phylogeography, cross-regional transmission, MSM, China, phylodynamics, viral epidemiology, Jiangsu, Hangzhou