Learn about
Syphilis
Syphilis is a bacterial STD caused by Treponema pallidum that progresses through distinct clinical stages if untreated. It is curable at any stage with antibiotics, but damage caused by late-stage disease cannot be reversed. After decades of decline, syphilis rates in the US have risen sharply since 2000 — the CDC reported over 200,000 cases in 2023, including a dramatic rise in congenital syphilis (transmission during pregnancy). Syphilis is now a significant public health concern across all demographics, not just specific risk groups.
Syphilis Symptoms
Syphilis is notoriously called "the great imitator" because it can mimic many other conditions. Primary syphilis: a single, painless sore (chancre) at the infection site, appearing 10–90 days after exposure. The chancre heals spontaneously in 3–6 weeks — many people never notice it, especially if it's internal or on the cervix or rectum. Secondary syphilis: appears 2–8 weeks after the chancre, with a rash (classically on the palms of the hands and soles of the feet), flu-like symptoms, swollen lymph nodes, and sometimes mouth sores. This stage also resolves without treatment. Latent syphilis: no symptoms, but the bacteria remain in the body. Tertiary syphilis: rare with modern antibiotic access, but causes severe damage to the heart, brain, and other organs in untreated cases.
Syphilis Transmission
Syphilis spreads through direct contact with a syphilitic sore (chancre) during vaginal, anal, or oral sex. Sores can occur on the genitals, anus, lips, or inside the mouth — if a sore is inside the mouth or rectum, transmission can occur without either partner knowing the sore exists. Syphilis cannot be transmitted through toilet seats, door handles, swimming pools, or shared utensils. Congenital syphilis — transmission from a pregnant person to their baby during pregnancy or delivery — can cause stillbirth, premature birth, or serious long-term health problems in the infant, and is the reason routine syphilis screening during pregnancy is mandatory in the US.
Syphilis Treatment
Syphilis is curable at any stage with antibiotics. The first-line treatment for primary, secondary, and early latent syphilis is a single intramuscular injection of benzathine penicillin G 2.4 million units. Late latent and tertiary syphilis require three weekly doses. Neurosyphilis requires IV penicillin G for 10–14 days. For people with penicillin allergy, doxycycline is an alternative for non-pregnant patients; pregnant patients with penicillin allergy should undergo penicillin desensitisation, as penicillin is the only proven treatment for preventing congenital syphilis. After treatment, follow-up serological testing is required to confirm adequate response.
Syphilis Health Risks
Untreated syphilis can progress to tertiary syphilis, causing gummatous disease (destructive granulomas in any organ), cardiovascular syphilis (aortic aneurysm, aortic regurgitation), or neurosyphilis (meningitis, stroke, dementia, and tabes dorsalis). These complications occur years to decades after initial infection and cause irreversible damage. Congenital syphilis causes miscarriage, stillbirth, or severe infant disease including bone damage, hepatosplenomegaly, neurological problems, and deafness. The US is currently experiencing a congenital syphilis crisis — cases have increased more than tenfold since 2012.
Syphilis Prevention
Consistent condom use reduces syphilis transmission risk but is not complete protection — sores in uncovered areas can still transmit the infection. Routine screening is essential: the CDC recommends syphilis testing at least annually for MSM, more frequently for those with multiple partners, and at every prenatal visit for pregnant women. Avoiding sexual contact during active syphilitic outbreaks reduces risk. Partner notification — informing all sexual partners from the past 90 days (primary) or 6 months (secondary) — is important and may be legally required in some states. There is no vaccine for syphilis.
Syphilis Diagnosis
Syphilis is diagnosed through blood tests using a two-test approach: an initial non-treponemal test (RPR or VDRL) for screening, confirmed by a treponemal test (FTA-ABS or TPPA). Some labs use a reverse sequence (treponemal first), which may detect past treated infections. During primary syphilis, serology may still be negative — swabbing the chancre for PCR or darkfield microscopy is more sensitive for active primary disease. The window period for serology is approximately 2–4 weeks after exposure. RPR titre is used to monitor treatment response — a fourfold decline at 6–12 months after treatment indicates adequate response.
Syphilis Complications
Tertiary syphilis complications — cardiovascular disease, neurosyphilis, and gummatous disease — are irreversible even after successful antibiotic treatment. Neurosyphilis can cause dementia, blindness, deafness, and loss of coordination. Cardiovascular syphilis can cause aortic aneurysm requiring surgery. Congenital syphilis complications include bone malformations, liver damage, neurological impairment, deafness, and interstitial keratitis causing blindness. The Jarisch-Herxheimer reaction — a transient fever and flu-like response occurring within 24 hours of starting penicillin — is common in early syphilis and should not be confused with antibiotic allergy.
Syphilis Post-Diagnosis Advice
Receive the full antibiotic course as prescribed — syphilis treatment cannot be shortened. Abstain from sex until treatment is complete and you and your partners have both been tested. Notify all sexual partners from the relevant window: 3 months for primary, 6 months for secondary, 1 year for early latent syphilis. Return for follow-up serological testing at 6 and 12 months after treatment (and 24 months for late latent or tertiary syphilis) — RPR titre should fall fourfold to confirm treatment success. If you're pregnant and diagnosed with syphilis, treatment should begin immediately: congenital syphilis is preventable with adequate prenatal treatment.
Syphilis FAQ
Can syphilis be cured?
Yes — syphilis is fully curable at any stage with appropriate antibiotics. Treatment with penicillin clears the infection. However, any organ damage caused by late-stage syphilis (tertiary disease) cannot be reversed by treatment. This is why early diagnosis and treatment are critical.
How soon after treatment can I resume sexual activity?
For primary and secondary syphilis treated with a single penicillin injection: abstain from sex for 7 days after treatment and until all partners have been treated. Your provider will schedule follow-up blood tests at 6 and 12 months to confirm the treatment worked — RPR titre should decline fourfold. Confirm with your provider before resuming sexual activity, as individual circumstances vary.