Is syphilis a sexually transmitted infection (STI)?

Syphilis is a sexually transmitted infection (STI) primarily spread through sexual contact. It can also be transmitted via contact with contaminated clothing of syphilitic patients, blood transfusion, or vertical transmission from mother to child.

Syphilis is a common STI caused by infection with the spirochete *Treponema pallidum*, resulting in a chronic, systemic infectious disease. Its main transmission routes include sexual contact, blood exposure, and mother-to-child (vertical) transmission. Following infection, localized skin and mucosal damage may occur—manifesting as dry skin, vesicles, or mucosal patches—and the disease may progress to involve the cardiovascular and nervous systems, potentially threatening life. Moreover, maternal syphilis infection during pregnancy can lead to intrauterine infection and increase the risk of preterm birth, spontaneous abortion, or stillbirth. Therefore, prompt diagnosis and active cooperation with medical treatment are essential.

In early-stage syphilis, treatment should follow physician guidance and typically involves intramuscular injection of benzathine penicillin, procaine penicillin, or ceftriaxone. For patients allergic to penicillin, doxycycline may be used as an alternative. If syphilis has caused cardiovascular involvement—such as coronary ostial stenosis—interventional procedures including coronary ostial dilation or endarterectomy may be required.