👉 In medicine, syphilis is a sexually transmitted infection (STI) that affects the immune system. It can occur in both men and women and is usually caused by the bacterium Treponema pallidum. Symptoms of syphilis include fever, chills, headache, fatigue, muscle pain, joint pain, stiffness, and persistent sores or lesions on the skin, genitals, or anal area. Treatment for syphilis typically involves antibiotics to treat the infection, but it can