Syphilis is a bacterial infection that is sexually transmitted. This is not as common as some of the other bacterial STIs but can lead to very serious health problems if it is left untreated.
Syphilis can be passed on by sharing sex toys as well as through vaginal, anal or oral sex (especially without a condom). It can also be passed from mother to baby during pregnancy.
As many people with Syphilis are unaware they have it, passing the infection on without realising it is common.