Syphilis is a sexually transmitted bacterial infection caused by the spirochete Treponema pallidum, which spreads primarily through sexual contact (vaginal, anal, or oral) with an infected person, but can also transmit from mother to fetus during pregnancy (congenital syphilis) or rarely via blood transfusion/shared needles. It progresses in stages if untreated: primary (painless sore or chancre at the infection site, usually genitals/anus/mouth, appearing 10–90 days after exposure and healing in 3–6 weeks); secondary (widespread non-itchy rash often on palms/soles, mucous patches in mouth, fever, sore throat, swollen lymph nodes, hair loss, or condyloma lata—highly contagious lesions); latent (no symptoms, but infection persists—early latent within 1 year, late latent after); and tertiary/late (years/decades later: gummas—destructive lesions on skin/bones/organs, cardiovascular issues like aortic aneurysm, or neurosyphilis affecting brain/nerves causing dementia, tabes dorsalis, or vision/hearing loss). Congenital syphilis in newborns can cause severe issues like rash, bone deformities, snuffles, hepatosplenomegaly, or stillbirth/miscarriage. Many cases are asymptomatic early on, making screening crucial. Diagnosis uses blood tests (e.g., nontreponemal like RPR/VDRL plus treponemal confirmation like FTA-ABS) or dark-field microscopy/PCR on lesions. It’s fully curable with antibiotics—typically a single intramuscular penicillin G injection for early stages, or multiple doses/longer courses (including IV for neurosyphilis) for later stages; alternatives exist for penicillin-allergic patients. Prevention involves consistent condom use, regular STI testing (especially for high-risk groups), partner notification/treatment, and prenatal screening. Untreated, it can lead to serious complications or death, but early detection and treatment prevent progression—see a doctor or sexual health clinic promptly if exposed or symptomatic.