Syphilis patients are the only source of infection. There are four ways of infection: direct contact infection, indirect contact infection, fetal syphilis and blood-borne infection. 1. Direct contact infection: sexual intercourse, kissing, homosexuality, mouth-to-genitalia contact and hand-to-genitalia contact with syphilis patients can all be infected with syphilis; 2. Indirect contact infection: contact with underwear, underwear, bedding, towels, razors, bath towels, bathtubs, toilets, etc. Syphilis patients may use contaminated treponema pallidum discharged from the damaged part of the patient, which may cause infection. 3. Fetal syphilis: Without treatment, female syphilis patients can circulate to the fetus through blood, so that the fetus can be infected with syphilis. 4. Blood-borne infection: If the blood donor is a latent syphilis patient, once it is imported into the recipient, infection will occur.