Syphilis is a sexually transmitted disease and its main cause is the infection of the body with the syphilis spirochete. The only source of infection for syphilis is the person with syphilis, whose blood, semen, skin lesions, breast milk and saliva can contain a certain number of syphilis spirochetes. An uninfected person can get infected if there is a slight break in the skin or mucous membrane during sexual contact with a syphilis patient. The infection is highly contagious 1-2 years after infection, and patients who have been infected for more than 4 years are basically non-contagious. In addition, syphilis infection can be transmitted from a pregnant woman to her fetus through the placenta. Usually after the fourth month of pregnancy, syphilis spirochetes can be transmitted from the mother to the fetus through the placenta, or during the delivery process due to abrasions on the head and shoulder, resulting in direct contact transmission. A small number of patients can also be infected through the medical route, by shaking hands or by contact with contaminated clothing or utensils.