Syphilis is an infection that’s most commonly transmitted through sexual contact. It typically starts out as a sore on the mucous membranes of the genitals or mouth. Contact with one of these sores can result in spread from one person to another. While it can be very dangerous if untreated, there are simple, effective treatments available that can clear up a case of syphilis quickly and easily. It’s important to get checked frequently, especially if you or your partner has sexual contact with multiple partners.