What is it?

Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum. It progresses through distinct stages — primary, secondary, latent, and tertiary — each with different symptoms. Syphilis is curable with antibiotics if detected early, but untreated syphilis can cause serious long-term health problems.

How it spreads

Syphilis spreads through direct contact with a syphilitic sore (chancre). Sores can be on the penis, vagina, anus, rectum, lips, and mouth. Transmission occurs during vaginal, anal, or oral sex. It can also pass from a pregnant person to their baby (congenital syphilis). Syphilis cannot be spread through casual contact — toilet seats, doorknobs, or clothing.

Symptoms

Syphilis progresses in stages:

  • Primary: A single painless sore at the infection site, lasting 3–6 weeks
  • Secondary (3–6 weeks later): Skin rash often on palms and soles, flu-like symptoms, mucous membrane sores
  • Latent: No symptoms
  • Tertiary (years later, if untreated): Serious damage to the heart, brain, nerves, and other organs

Testing

Syphilis is diagnosed with a blood test — either RPR (rapid plasma reagin) or VDRL (Venereal Disease Research Laboratory) as a screening test, confirmed by treponemal tests. Testing should be done 3 months after potential exposure for the most accurate results. The CDC recommends annual testing for people at higher risk.

Treatment

Syphilis is curable with penicillin G, given by injection. The stage of infection determines the dose and duration. People who are allergic to penicillin may be treated with doxycycline. Treatment kills the bacteria but cannot undo damage already done by late-stage syphilis. Partners from the last 90 days (primary) or last year (secondary) should be tested.

Prevention

Prevention steps:

  • Use condoms consistently during all sexual activity
  • Get tested regularly — especially if you have new or multiple partners
  • If pregnant, get tested for syphilis at the first prenatal visit

Doxycycline post-exposure prophylaxis (doxy-PEP) is an emerging option for high-risk individuals — talk to a doctor.