Syphilis moves through four stages. The primary stage brings a painless sore (chancre) at the infection site about three weeks after exposure. The secondary stage adds a body rash, often on the palms and soles, plus fever and swollen glands. The latent stage is silent. The tertiary stage can damage the heart, brain, and nerves years later.
~3 wks; 10–90 days
by stage
| Item | Value |
|---|---|
| Primary sore | painless — ~3 wks; 10–90 days |
| Testing | 2 blood tests |
| Treatment | penicillin — by stage |
| Symptoms fade | ≠ cured |
What syphilis is
Syphilis is a bacterial infection caused by Treponema pallidum, a corkscrew-shaped organism that burrows through mucous membranes and broken skin, then spreads through the bloodstream to the rest of the body. It is curable with the right antibiotics CDC, About Syphilis. It's dangerous because it hides: each stage's symptoms fade on their own, so people feel cured while the infection moves deeper. After a steep climb, there were about 53,000 primary-and-secondary cases in 2023, and the late or unknown-duration stage nearly doubled in rate between 2020 and 2023 CDC AtlasPlus, 2023.
Symptoms by stage — and the silent reality
Understand one thing above all: symptoms going away does not mean the infection is gone. Whether or not you're treated, the sores and rash resolve on their own, and without antibiotics the infection advances to the latent and possibly tertiary stages. That false reassurance is why syphilis gets missed.
Primary syphilis
The first sign is a chancre: one or more firm, round, painless ulcers at the exact spot the bacteria entered, whether the penis, vagina, anus, rectum, lips, or mouth. It appears roughly three weeks after exposure, though the incubation period runs anywhere from about ten days to three months. Because the sore is painless and frequently tucked inside the vagina, anus, or mouth, many people never notice it. It heals over three to six weeks with or without treatment, leaving the infection in place.
Secondary syphilis
As the bacteria spread through the blood, a rough red or reddish-brown rash develops. Its signature is showing up on the palms and soles, though it can cover the trunk too. Alongside the rash you may see moist, wart-like lesions on mucous membranes, plus fever, swollen lymph nodes, sore throat, patchy hair loss, headache, weight loss, muscle aches, and deep fatigue. These symptoms also fade on their own, and that resolution does not mean the infection is cured.
Latent syphilis
The latent stage has no symptoms at all, but the bacteria persist and the infection is still detectable on a blood test. Clinicians split this stage by time because it dictates treatment: early latent means infection acquired within the preceding twelve months (documented by a recent seroconversion, a fourfold titer rise, or recent primary/secondary signs), and late latent or unknown duration covers everything older.
Tertiary syphilis
In untreated cases, tertiary disease can surface roughly 10 to 30 years after infection, though that window isn't guaranteed symptom-free and some damage appears sooner. It attacks the heart and blood vessels (cardiovascular syphilis), forms destructive soft-tissue masses called gummas, and injures the brain and nervous system. Tertiary syphilis can be fatal.
Two complications break the neat stage timeline entirely. Ocular syphilis (infection of the eye, which can cause vision loss) and neurosyphilis (invasion of the brain and spinal cord) can both occur at any stage. New vision changes, severe headache, confusion, or weakness in someone with syphilis is a medical emergency StatPearls, Syphilis.
How syphilis spreads
Syphilis passes through direct contact with a syphilis sore during vaginal, anal, or oral sex, so the secondary rash and primary chancre are highly contagious. It also crosses from a pregnant person to the baby during pregnancy. Beyond the immediate risk, having syphilis roughly doubles the chance of acquiring HIV, because the open sores give the virus an easy entry point.
Congenital syphilis
Mother-to-baby transmission is among the most preventable harms in this field, and it's surging. Cases nearly doubled in four years, from 2,163 in 2020 to 3,882 in 2023, a 77% rise and the highest level in decades, with nearly 4,000 cases in 2024 CDC, Congenital Syphilis. Untreated syphilis in pregnancy harms the baby in 50 to 80% of cases: miscarriage, stillbirth, newborn death, prematurity or low birth weight, deformed bones, anemia, and brain or nerve damage causing blindness or deafness. Prenatal screening plus penicillin prevents nearly all of it.
How syphilis is tested
Testing is a simple blood draw, but diagnosis takes two serologic tests: a nontreponemal test (RPR or VDRL) and a treponemal test (TP-PA, FTA-ABS, EIA, or CIA) CDC Lab Recommendations, 2024. Labs run them in one of two acceptable orders: the traditional algorithm (nontreponemal screen first, treponemal confirm) or the reverse-sequence algorithm (treponemal first, then a quantitative nontreponemal test).
Timing matters. Antibodies can take up to about two weeks after the chancre shows up to appear, and the chancre itself doesn't appear until roughly three weeks after exposure. A test done very early can be falsely negative. If your exposure was recent and the test is negative, retest. For exact timing, see when to test after exposure, and you can get tested or compare testing providers to find an option that fits.
On who should be screened: USPSTF gives a Grade A recommendation for early, universal screening of all pregnant persons regardless of risk, at the first opportunity, even at delivery if missed earlier USPSTF, Pregnancy. For nonpregnant adolescents and adults, USPSTF (2022, Grade A) recommends screening people at increased risk, including men who have sex with men, people with HIV or other STIs, and those with a history of incarceration or sex work USPSTF, 2022.
How syphilis is treated
Penicillin G treats every stage, and it has no dependable oral substitute CDC Tx Guidelines. The dose follows the stage. Primary, secondary, and early latent syphilis are treated with a single intramuscular injection of benzathine penicillin G (2.4 million units) CDC, Primary & Secondary. Late latent, unknown-duration, and tertiary syphilis require three weekly injections (7.2 million units total) CDC, Latent Syphilis. Neurosyphilis, ocular, and otosyphilis need intravenous aqueous crystalline penicillin G in the hospital for 10 to 14 days CDC, Neurosyphilis.
Getting the product right has prevented real treatment failures: use benzathine penicillin G (Bicillin L-A). The combination product Bicillin C-R is not an acceptable substitute. For documented penicillin allergy in non-pregnant adults, doxycycline is the standard alternative, though a longer course is required for late latent disease, and azithromycin is not recommended because of resistance. In pregnancy there is no safe alternative: an allergic patient must be desensitized and given penicillin, the only treatment that protects the baby. Over 90% of people who believe they're penicillin-allergic actually are not.
A short, harmless reaction often follows the first dose. The Jarisch-Herxheimer reaction brings fever, chills, headache, and muscle aches within the first 24 hours, the result of dying bacteria releasing inflammatory signals rather than an allergy. It affects roughly 95% of people treated for secondary syphilis and settles within about a day StatPearls, JHR.
Cure is confirmed by blood titers, not by feeling better. Clinicians repeat quantitative RPR/VDRL at 6 and 12 months for primary and secondary syphilis, and again at 24 months for latent disease. A fourfold or greater drop, say 1:32 falling to 1:8, confirms success, while a fourfold rise signals failure or reinfection. So can you get syphilis again after treatment? Past treatment gives no immunity.
| Stage | Hallmark symptoms | Standard treatment |
|---|---|---|
| Primary | Painless chancre at infection site | Single benzathine penicillin G injection |
| Secondary | Rash on palms/soles, fever, swollen glands | Single benzathine penicillin G injection |
| Early latent (<1 yr) | No symptoms; detectable by blood test | Single benzathine penicillin G injection |
| Late latent / unknown | No symptoms | Three weekly penicillin injections |
| Tertiary | Heart, vessel, brain, and nerve damage | Three weekly injections (IV if neuro/ocular) |
Complications if syphilis is left untreated
Untreated, syphilis works its way into vital organs over years:
- Cardiovascular syphilis — damage to the heart and the aorta, the body's main artery, which can weaken and rupture.
- Gummas — soft, destructive growths that erode skin, bone, and internal organs.
- Neurosyphilis — infection of the brain and spinal cord, causing confusion, paralysis, dementia, or stroke; it can strike at any stage.
- Ocular syphilis — eye involvement that can lead to permanent vision loss.
- Congenital syphilis — stillbirth, newborn death, or lifelong disability in the baby.
How to prevent syphilis
The basics are correct and consistent condom use, mutual monogamy with a partner who has tested negative, and routine screening for anyone at increased risk. There's also a newer tool, DoxyPEP: a 200 mg dose of doxycycline within 72 hours after sex reduced syphilis acquisition by about 73% in trials, and CDC (2024) recommends it through shared decision-making for men who have sex with men and transgender women who had a bacterial STI in the past year CDC DoxyPEP, 2024. For pregnant people, the highest-yield prevention is early prenatal screening plus penicillin. See our full guide on how to prevent syphilis for the complete strategy.
When to see a clinician
Get evaluated promptly if you notice a painless sore anywhere on the genitals, anus, or mouth; a rash on your palms or soles; or unexplained fever and swollen glands after a possible exposure. Test if you've had a partner diagnosed with syphilis, even with no symptoms. Treat new vision changes or neurological symptoms — confusion, severe headache, weakness — as an emergency. If you're pregnant, ask for syphilis screening at your first prenatal visit, no exceptions.