Syphilis is a chronic sexually transmitted infection caused by the bacterium Treponema pallidum. It has multiple stages and symptoms that can vary or be asymptomatic depending on the stage. It is most commonly spread through sexual contact but can also be transmitted from mother to child. While it was historically treated with toxic mercury, syphilis can now be easily cured with antibiotics like penicillin if treated during early stages. However, treatment does not reverse prior damage caused by the infection.