Syphilis

Syphilis is an infectious disease caused by Treponema pallidum, described in the source material as a gram-negative, spirochete bacterium ^[1]. It is a sexually transmitted infection and may also be acquired congenitally during pregnancy through transplacental transmission ^[1][3]. Source-backed detail on other etiologic variants or additional disease classifications is not yet available beyond this bacterial, sexually transmitted characterization ^[1].

The source material describes early syphilis as occurring within the first year after infection and including symptomatic primary and secondary stages as well as asymptomatic early latent infection ^[1]. Primary syphilis is characterized by painless anogenital lesions, while secondary syphilis is associated with a diffuse rash, mucocutaneous lesions, and lymphadenopathy ^[1]. Late syphilis, diagnosed more than a year after infection, includes asymptomatic late latent disease and symptomatic tertiary disease ^[1]. Neurosyphilis can occur at any stage and may lead to meningitis, uveitis, hearing loss, or stroke ^[1]. In pregnancy, in-utero exposure is associated with severe fetal outcomes, including stillbirth or death during infancy in up to 40% of exposed fetuses according to the cited review ^[1].

Syphilis is described as endemic worldwide, with the literature noting that bacterial sexually transmitted infections remain common causes of global ill health and that social, economic, and behavioural factors are key determinants of prevalence ^[2][3]. An estimated 8 million adults aged 18 to 49 years acquired syphilis globally in 2022 ^[1]. The source material also reports substantial recent increases in the United States from 2019 to 2023, including a 61% overall rise in cases, a 112% increase in diagnoses among females, and a 106% increase in congenital syphilis cases ^[1]. In high-income countries, the incidence of early syphilis is again increasing, and congenital syphilis elimination is identified as a specific public-health target requiring enhanced surveillance and coordinated action ^[2].

Syphilis is transmitted through contact with infectious lesions during vaginal, anal, or oral sex ^[1]. It can also be transmitted vertically via the placenta during pregnancy ^[1]. The source material additionally notes that sexually acquired syphilis commonly coexists with at least one other sexually transmitted infection, but detailed transmission persistence or environmental routes are not supported in the provided snippets ^[3].

The provided sources identify increased risk among people with HIV, persons engaging in condomless sex with multiple partners, and men who have sex with men ^[1]. The review also notes that men who have sex with men accounted for 32.7% of all males with primary and secondary syphilis in 2023 ^[1]. Pregnant women are specifically highlighted in the CDC STI guideline summary as a group for expanded syphilis testing consideration, reflecting concern for congenital infection ^[4].

Prevention in the source material centers on public-health and sexual-health control measures rather than patient-level treatment advice ^[4]. CDC STI guidelines are described as providing recommendations for persons who have or are at risk for sexually transmitted infections, including expanded risk factors for syphilis testing among pregnant women ^[4]. The literature also emphasizes that reducing congenital syphilis requires coordinated multiagency approaches, enhanced surveillance, and reliable access to appropriate penicillin supplies ^[2].

For surveillance purposes, syphilis should be interpreted as a disease with both sexual and congenital transmission pathways, and recent trends suggest rising burden in several settings ^[1][2]. The source material highlights increasing early syphilis incidence in many high-income countries and substantial recent growth in U.S. cases, including congenital syphilis ^[1][2]. Monitoring should therefore track stage-specific cases, pregnancy-associated infection, and congenital outcomes, while recognizing that source-backed detail on optimal analytic case definitions is not yet available ^[1][2].

1. 1 Chevalier FJ et al. Syphilis: A Review. JAMA. 2025 Dec 2. PMID: 41100079. doi: 10.1001/jama.2025.17362. PubMed: https://pubmed.ncbi.nlm.nih.gov/41100079/
2. 2 Syphilis and Congenital Syphilis. Rook's Textbook of Dermatology. 2024. doi: 10.1002/9781119709268.rook029. DOI: https://doi.org/10.1002/9781119709268.rook029
3. 3 Syphilis and Congenital Syphilis. Rook's Textbook of Dermatology, Ninth Edition. 2016. doi: 10.1002/9781118441213.rtd0030. DOI: https://doi.org/10.1002/9781118441213.rtd0030
4. 4 Workowski KA et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021 Jul 23. PMID: 34292926. doi: 10.15585/mmwr.rr7004a1. PubMed: https://pubmed.ncbi.nlm.nih.gov/34292926/
5. 5 Stafford IA et al. Syphilis Complicating Pregnancy and Congenital Syphilis. N Engl J Med. 2024 Jan 18. PMID: 38231625. doi: 10.1056/NEJMra2202762. PubMed: https://pubmed.ncbi.nlm.nih.gov/38231625/
6. 6 Syphilis Osseuse (Syphilis Acquise). Journal of the American Medical Association. 1908. doi: 10.1001/jama.1908.02540230083027. DOI: https://doi.org/10.1001/jama.1908.02540230083027

ICD-10

A50-A53

ICD-11

1A70

Total cases

8.5M

Total deaths

1K

Peak month

2024-03

Coverage

5 reporting countries · 2000-01-01 → 2026-06-01