The syphilis-causing bacterium is able to pass through intact mucous membranes or compromised skin, and is primarily transmitted during sexual contact, or during pregnancy or childbirth from an infected mother to her infant. Transmission can occur by kissing near a lesion (chancre), and through oral, vaginal, and anal sex.
Syphilis transmission through sharing needles appears to be limited, and transmission does not often occur through sharing of utensils, or contaminated toilet seats, hot tubs etc.
Condom use helps reduce the risk of syphilis transmission. However, if the condom does not cover a syphilis chancre, transmission can still occur during sexual contact.
Congenital syphilis occurs when an infected pregnant woman passes syphilis to her baby during pregnancy. For infected infants, treatment must begin immediately to prevent developmental delays, seizures, and other fatal complications.