Infectious syphilis

Syphilis is a sexually transmitted bacterial infection that progresses through primary, secondary, latent, and tertiary stages; the term "infectious syphilis" refers specifically to the primary, secondary, and early latent phases, which constitute the transmissible clinical window. The disease can also be passed from a pregnant person to the fetus, resulting in congenital syphilis.^[1][2]

Primary syphilis typically presents as a single firm, round, painless sore at the site of inoculation that resolves in three to six weeks, while secondary syphilis produces a range of mucocutaneous and systemic manifestations. Stage-specific signs and symptoms vary.^[1]

Syphilis is a commonly notified sexually transmitted infection whose reported trends depend strongly on screening intensity and case definitions. In the United States, infectious syphilis case counts have risen steadily since 2000, with the highest rates among men who have sex with men, of whom approximately half are co-infected with HIV. Increasing infectious syphilis among women of childbearing age—driven by rising rates in the general population, particularly among Indigenous and marginalized groups—has been linked to a parallel resurgence of congenital syphilis in middle- and higher-income countries.^[1][2]

Transmission occurs through sexual contact with infectious lesions of primary or secondary syphilis, and a pregnant person can transmit the infection to the fetus during pregnancy. Because lesions can occur on skin or mucosa not covered by a condom, barrier protection reduces but does not eliminate sexual transmission risk.^[1]

Prevention rests on testing, prompt treatment of identified infections, reduction of sexual exposure risk, and correct condom use. In pregnancy, a single antenatal test is considered insufficient; more frequent testing is recommended even for women deemed to be low risk, with immediate treatment of those who test positive to prevent congenital syphilis. A coordinated public-health approach emphasizes education, accessible antenatal care, updated guidelines, and follow-up of exposed infants.^[1][2]

1. 1US Centers for Disease Control and Prevention. About Syphilis | Syphilis | CDC [Internet]. cited 3 Sept 2026.Available from: https://www.cdc.gov/syphilis/about/
2. 2Thean L et al. New trends in congenital syphilis: epidemiology, testing in pregnancy, and management. Curr Opin Infect Dis. 2022 Oct 1. PMID: 36066379. doi: 10.1097/QCO.0000000000000875.PubMed: https://pubmed.ncbi.nlm.nih.gov/36066379/
3. 3Marra CM et al. Neurosyphilis. Continuum (Minneap Minn). 2015 Dec. PMID: 26633785. doi: 10.1212/CON.0000000000000250.PubMed: https://pubmed.ncbi.nlm.nih.gov/26633785/