Syphilis

Syphilis is a bacterial sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. It is classified under ICD-10 codes A50-A53 and ICD-11 code 1A70 as a preventable and curable infection that results in substantial morbidity and mortality when left untreated. The disease has been recognized for its ability to mimic multiple other conditions, earning the historical designation as 'the great imitator' due to its varied clinical presentations across different stages.

Syphilis presents in four stages: primary, secondary, latent, and tertiary. The primary stage typically manifests as a single firm, painless, non-itchy chancre with a clean base and sharp borders, usually 1-2 cm in diameter, appearing 2-6 weeks after exposure at the site of inoculation. Secondary syphilis, occurring approximately 4-10 weeks later, features a symmetrical reddish-pink, non-itchy rash frequently involving the palms and soles, along with potential mucous membrane lesions and condyloma latum. Latent syphilis is characterized by serologic evidence of infection without symptoms and can persist for years, divided into early latent (less than 2 years) and late latent phases. Tertiary syphilis may develop 3-15 years after initial infection in approximately one-third of untreated cases, presenting as gummatous disease, neurosyphilis, or cardiovascular complications; however, individuals with tertiary disease are not infectious.

Source-backed geographic distribution and outbreak context detail is not yet available in the provided source material. The infection is maintained through sexual transmission networks and can persist in populations with limited access to screening and treatment services. The substantial surveillance burden relates to the often-asymptomatic nature of infection, requiring laboratory-based detection strategies and partner notification protocols to interrupt transmission chains effectively.

Syphilis is transmitted through direct sexual contact with infectious lesions during oral, vaginal, or anal sex, via blood transfusion, and from mother to fetus during pregnancy or at birth. The bacterium is present in infectious lesions such as chancres and secondary-stage rashes, which can transmit infection if not covered by barrier protection. Mother-to-child transmission can result in congenital syphilis, with adverse outcomes occurring in an estimated 50-80% of untreated maternal infections depending on the stage of maternal syphilis.

Source-backed detail on specific high-risk groups is not yet available in the provided source material beyond the general characterization of sexually active individuals and pregnant women as priority populations for screening.

Primary prevention relies on correct and consistent use of condoms during sexual contact, though transmission can occur from areas not covered by condoms including genitals, anus, and mouth. Secondary prevention through screening is critical: rapid diagnostic tests can provide results within minutes, enabling immediate treatment initiation on the same clinical visit. Pregnant women should be tested at the first prenatal care visit and treated promptly if positive, as congenital syphilis is preventable through maternal penicillin treatment. Individuals diagnosed with syphilis should notify sexual partners to prevent new infections, and those at higher risk should be tested at least annually.

Surveillance for syphilis requires awareness that many infections are asymptomatic or present with minimal symptoms that escape clinical notice. Laboratory testing, including rapid point-of-care tests, serologic assays, and where available dark-field microscopy, forms the foundation of case identification. The staged nature of disease progression has implications for monitoring: early latent syphilis remains infectious with up to 25% of individuals experiencing recurrent secondary infection, while late latent and tertiary stages are not considered infectious. Congenital syphilis surveillance requires examination of all live-born or stillborn infants of women with syphilis, with follow-up serologic testing at monthly intervals for 3 months due to passive maternal antibody transfer.

1. 1 WHO Health Topics. Syphilis  -- Global.
2. 2 WHO Fact Sheet. Syphilis.
3. 3 WHO Q&A. News.
4. 4 Wikidata. syphilis.
5. 5 Wikipedia. Syphilis - Wikipedia.

ICD-10

A50-A53

ICD-11

1A70

Total cases

8.4M

Total deaths

1K

Peak month

2024-03

Coverage

3 reporting countries · 2000-01-01 → 2026-05-02