Syphilis is a sexually transmitted infection (STI) caused by the bacterium Treponema pallidum. It progresses in stages—primary, secondary, latent, and tertiary—each with distinct symptoms. In the primary stage, a painless sore (chancre) appears at the infection site, typically the genitals, mouth, or rectum, which may go unnoticed. During the secondary stage, symptoms may include skin rashes, mucous membrane lesions, fever, swollen lymph nodes, sore throat, and fatigue. If untreated, syphilis enters a latent phase with no visible symptoms but can still cause damage internally. In the final, tertiary stage, syphilis can lead to severe health complications, affecting the heart, brain, and other organs, potentially becoming life-threatening.

Syphilis is treatable with antibiotics, typically penicillin, especially in the early stages. Early diagnosis and treatment are crucial to prevent long-term damage, and regular screening is recommended for sexually active individuals to reduce the risk of spreading the infection. Practicing safe sex by using condoms and having open conversations about STI status with partners can help prevent transmission.