Syphilis is a sexually transmitted disease caused by the pale spirochete and is mainly transmitted through sexual intercourse, but can also be transmitted to the fetus through the placenta. The source of syphilis infection is the patient with syphilis, and the main ways of transmission are: 1. transmitted by sexual contact. Untreated patients in the first year after infection is the most infectious, these patients have a large number of syphilis spirochetes on the surface of the skin and mucous membrane damage, in the process of sexual intercourse is easy through the skin and mucous membrane minor damage to each other. 2, transmitted through the placenta. Pregnant women with syphilis, the pathogen can be infected through the placenta to the fetus. 3.Infection through blood transfusion. If the blood donor is in the window stage of syphilis infection (both the initial stage of syphilis spirochete infection, the patient’s immune system has not yet had time to produce antibodies, when laboratory tests are negative), the blood donated in this case may be transfused to the recipient as healthy blood. Patients infected through this route do not develop a hard chancre, but directly develop second-stage syphilis. 4. Other routes. In a few cases, syphilis can infect others through direct contact (e.g. kissing, breastfeeding, etc.), or indirect contact with everyday objects of patients with infectious damage (e.g. clothes, towels, razors, utensils, etc.).