Syphilis is a sexually transmitted infection (STI) caused by the bacterium Treponema pallidum. The first visible sign of the infection is a small sore (called a chancre) on the genitals, anus, or mouth. Blood tests are used to detect syphilis and it is treated with antibiotics. Consistent correct use of condoms, practicing long-term monogamy, and abstinence are the best ways to protect yourself against syphilis and other STIs.

Frequently Asked Questions

  • Is syphilis curable?

    Yes, syphilis can be treated with antibiotics, however, any damage done by the infection may not be reversible. Syphilis is commonly treated with a series of intramuscular injections of penicillin. For people who are allergic to penicillin, an alternative antibiotic may be effective.

  • What does a syphilis sore look like?

    A syphilis sore, known as a chancre, begins as a painless, firm, round bump on or near the genitals, anus, rectum, or mouth. There is usually only one sore, though more are possible, and chancres may be hidden inside the vagina or under the foreskin. A chancre may be mistaken for an ingrown hair or pimple, however, a chancre is not tender to the touch. Chancres sometimes break open and weep.

  • How do you get syphilis?

    Syphilis is a sexually transmitted infection that is spread through intimate contact with an infected partner. Infection occurs when skin or mucosal tissue comes in contact with an open, ulcerative chancre. Routinely practicing safer sex can reduce your risk of contracting syphilis.

  • Is syphilis a virus?

    No, syphilis is not a virus. Syphilis is a bacterial infection caused by a spiral-shaped bacterium called Treponema pallidum. Unlike a viral infection that needs to run its course, syphilis can be treated with antibiotics.

  • Where did syphilis come from?

    Syphilis was first discovered in the early 16th century in Europe and was commonly referred to as the pox. Scholars believe it possibly existed prior to that and may have been mistaken as a type of leprosy. The origin of Treponema pallidum, the bacterium responsible for syphilis infections, is unclear, but may have mutated from a strain found in sheep or cattle.

  • What happens if syphilis is left untreated?

    Syphilis is a bacterial infection that, left untreated, progresses through stages that may eventually lead to blindness, dementia, and death. Primary stage syphilis lasts three to six weeks. Secondary stage syphilis, characterized by an itchless body rash, lasts several months. Within a year, syphilis enters a symptom-less latent stage. Decades later, tertiary stage syphilis can result in multiple organ damage.

  • Does syphilis stay with you for life?

    Syphilis is a sexually transmitted bacterial infection that can be successfully treated with antibiotics. However, syphilis can go undetected and remain dormant in the body for decades. While the infection can be treated, damage caused by the illness cannot be reversed.

  • How is syphilis diagnosed?

    Syphilis is diagnosed through blood tests that detect antibodies to the bacterium Treponema pallidum. The antibodies, proteins produced by the body in response to an infection, remain in the bloodstream for years, and lab analysis can provide clues to when the infection occurred. Testing can be done at a doctor’s office, sexual health clinic, or at home with a kit purchased at a drug store or online.

Key Terms

Page Sources
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  1. O’Byrne P, MacPherson P. Syphilis. BMJ. 2019;365:l4159. doi:10.1136/bmj.l4159

  2. Centers for Disease Control and Prevention. Syphilis – CDC fact sheet (detailed). Updated January 30, 2017.

  3. US National Library of Medicine: MedlinePlus. Congenital syphilis. Updated October 8, 2020.

  4. US National Library of Medicine: MedlinePlus. Sexually transmitted diseases. Updated September 29, 2020.

Additional Reading