Syphilis is caused by the bacterium Treponema pallidum and is passed on through direct contact with a (often unnoticed) sore or rash during vaginal, anal or oral sex. A pregnant person can also pass the infection to their baby. In 2024 the Centres for Sexual Health recorded almost 1,800 infectious syphilis diagnoses — the highest figures in years. Most are among men who have sex with men, but numbers are rising among women and heterosexual men too.
The stages of syphilis
Syphilis runs in stages, and because the symptoms fade on their own in between, the infection is often called "the great imitator". Without treatment you stay infected, even when you no longer notice anything.
- Primary stage (10–90 days, on average 3 weeks after infection): a single painless, firm ulcer (the "chancre") on the penis, vagina, anus or in the mouth. It heals on its own in 4–6 weeks — but you are still infected.
- Secondary stage (weeks to months later): a non-itchy rash, often including the palms and soles, with fever, fatigue and swollen lymph nodes. These symptoms also fade on their own.
- Latent stage: no symptoms, but the bacterium is still present. In the first year (early latent) you are still infectious.
- Late stage (years later, rare with treatment): lasting damage to the heart, blood vessels, brain or nervous system (neurosyphilis).
Testing: a blood test
Syphilis is detected with a blood test (serology). It is usually reliable from about six weeks after the risk contact; in the very early primary stage the result can still be negative, so a repeat test follows if there is any doubt. If there is a fresh ulcer, a clinician can test material from it directly (PCR), often before the blood test turns positive. Syphilis and HIV are frequently tested together, because they often occur together.
Treatment: a penicillin injection
Syphilis is very treatable with penicillin. For an early infection (less than a year old) a single injection of benzathine benzylpenicillin into the buttock muscle is usually enough; for a longer-standing infection or one of unknown duration it is three injections, each a week apart. With a penicillin allergy, doxycycline tablets are given instead (not during pregnancy). Neurosyphilis is treated in hospital with intravenous penicillin. Treatment runs via the GGD, a dermatologist or the GP.
Partner notification and follow-up
Notify your sexual partners so they can get tested; how far back you go depends on the stage and can be one to two years for syphilis. Avoid sex until the ulcers or rash have fully gone and treatment is complete. After treatment the clinician checks with blood tests — usually at 3, 6 and 12 months — whether the infection has truly cleared; the amount of antibodies (the titre) should drop clearly.
Pregnancy and congenital syphilis
In the Netherlands every pregnant woman is screened for syphilis as standard early in pregnancy. This matters, because an untreated infection can lead to miscarriage, premature birth or congenital syphilis in the baby. Timely treatment with penicillin protects both mother and child.
This information is general and was compiled with care from public sources, but it does not replace medical advice. For symptoms or doubt, always consult a doctor.
