Syphilis
Symptoms, Causes & Treatment
Understanding syphilis: its stages, why rates are rising in the UK, how it is diagnosed at each stage, and why prompt treatment is critical.
What Is Syphilis?
Syphilis is a bacterial sexually transmitted infection (STI) caused by the spirochaete bacterium Treponema pallidum. Once considered a disease of the past, syphilis has made a dramatic resurgence in the UK and globally. Cases in England have risen sharply, with over 8,000 diagnoses annually in recent years -- the highest rates since the 1940s.
Syphilis is known as "the great imitator" because its symptoms can mimic many other conditions, making clinical diagnosis challenging. If left untreated, syphilis progresses through distinct stages over months to years and can ultimately cause devastating damage to the heart, brain, and nervous system (tertiary syphilis). However, it is easily diagnosed with a blood test and fully curable with penicillin, particularly when caught early.
Syphilis is most prevalent among men who have sex with men (MSM) but is increasing in heterosexual populations as well. Congenital syphilis (transmission from mother to baby during pregnancy) remains a serious concern and is entirely preventable with antenatal screening and treatment.
What Are the Symptoms of Syphilis?
Syphilis presents differently at each stage. Knowing the staged presentation helps both clinicians and patients recognise it early.
Primary: painless sore (chancre) on genitals, mouth, or anus · Secondary: widespread rash (including palms/soles), fever, hair loss, condylomata lata · Latent: no symptoms, positive blood test · Tertiary: gummas, cardiovascular syphilis, neurosyphilis (rare)
Neurosyphilis: headache, vision changes, hearing loss, personality change · Cardiovascular syphilis: aortic aneurysm, aortic regurgitation · Congenital syphilis in pregnancy — all syphilis in pregnancy requires immediate specialist treatment · Any stage syphilis requires contact tracing
Syphilis in pregnancy requires immediate specialist referral and treatment to prevent congenital syphilis. Neurological or cardiovascular symptoms in any patient with known or suspected syphilis require emergency assessment.
What Causes Syphilis?
Syphilis is caused by Treponema pallidum, a spirochaete bacterium. It is a complex, staged disease that mimics many other conditions — earning its historical name of ‘the great imitator’.
Treponema pallidum cannot be cultured in the lab. It is diagnosed entirely through clinical findings and serology. The organism invades the CNS early in infection — even in primary and secondary stages.
Syphilis rates in the UK have increased dramatically since 2010, particularly among MSM. Co-infection with HIV is common and syphilis significantly increases HIV transmission efficiency.
STIs are transmitted through unprotected vaginal, anal, or oral sex. Some (herpes, HPV, syphilis) can spread through skin-to-skin contact even without penetration or visible symptoms.
Many STIs, particularly chlamydia, gonorrhoea, and early HIV, cause no symptoms at all. Regular testing is the only way to detect them — waiting for symptoms means delayed treatment and onward transmission.
Condoms reduce STI transmission by 85–98% when used consistently and correctly. They are less effective for infections spread by skin contact (herpes, HPV, syphilis) where lesions extend beyond the condom-covered area.
STI co-infection is common. Gonorrhoea and chlamydia frequently co-exist (15–40% co-infection rate). HIV significantly increases susceptibility to all other STIs and their complications.
Key Risk Factors
How Is Syphilis Diagnosed?
Syphilis is diagnosed by blood tests detecting treponemal and non-treponemal antibodies. In primary syphilis with an active chancre, serology may be negative — darkfield microscopy of chancre exudate can provide immediate diagnosis. All stages of syphilis require specialist sexual health management and contact tracing.
How Is Syphilis Treated?
Syphilis is highly treatable at all stages with penicillin. The stage determines the dose and duration of treatment.
Supportive Measures
All syphilis at any stage requires management by a specialist sexual health clinic. Contact tracing of all partners from the appropriate lookback period is mandatory. A Jarisch-Herxheimer reaction (fever, rigors within 24 hours of penicillin) is expected in early syphilis and is managed with paracetamol — it is not an allergic reaction.
Syphilis Reinfection & Follow-Up
Past syphilis infection does not confer lasting immunity — reinfection is common. Following treatment, serological monitoring (RPR titre) every 3 months for 1 year confirms response to treatment. Rising titres indicate reinfection or treatment failure and require reassessment. In HIV-positive patients, more intensive follow-up is required.
When Should You Seek Help for Syphilis?
Neurological symptoms with known syphilis history (neurosyphilis) · Cardiovascular symptoms in late syphilis · Syphilis in pregnancy — all require immediate specialist referral · Jarisch-Herxheimer reaction after first penicillin dose (fever, rigors) — anticipated and managed in clinic.
You have a painless sore on your genitals, mouth, or anus · You have a non-itchy widespread rash · A partner has been diagnosed with syphilis · You are pregnant and have not had antenatal syphilis screening · You are HIV-positive and have not been screened recently.
How to Prevent Syphilis
Syphilis prevention uses the same tools as all STI prevention — with particular attention to regular screening in high-risk groups.
Annual STI testing is recommended for all sexually active people. Those with multiple partners should test every 3 months. Free NHS testing is available at sexual health clinics, online via SHGM/SH:24, and from GP surgeries.
Use condoms consistently for vaginal, anal, and oral sex with new or casual partners. Dental dams reduce transmission during oral-vulval contact. Lube reduces condom breakage and anal mucosal trauma.
Notify all recent sexual partners when diagnosed with an STI so they can be tested and treated. Partner notification can be done directly or anonymously through the sexual health clinic (contact tracing service).
HPV vaccination prevents 90% of cervical cancer and most genital warts. Hepatitis B vaccine is recommended for all MSM, PWID, and sexual health clinic attendees not previously vaccinated.
PrEP (Truvada or Descovy) is available free on the NHS at sexual health clinics for eligible high-risk individuals. It is over 99% effective when taken as prescribed. Regular HIV and kidney function testing is required during use.
If you are HIV-positive and on effective ART with an undetectable viral load, you cannot transmit HIV to sexual partners (U=U — Undetectable = Untransmittable). This is one of the most important advances in HIV medicine.
Speak to a Clinician About Syphilis Testing
Through The GP Service, a clinician can arrange syphilis blood testing, advise on management, and refer to a specialist sexual health clinic for treatment — all online.
Expert clinical advice, when you need it.
Syphilis FAQs
Syphilis in pregnancy can cause miscarriage, stillbirth, premature birth, and severe congenital syphilis in the newborn (causing bone, liver, brain, and skin disease). All pregnant women in the UK are offered a syphilis blood test at their first antenatal appointment. Treatment with benzathine penicillin G during pregnancy is safe and highly effective at preventing mother-to-child transmission. If you are pregnant and believe you may have been exposed to syphilis, seek urgent testing and treatment. Contact tracing of all recent partners is mandatory. Untreated syphilis in pregnancy is one of the most preventable causes of neonatal death.
STI testing is recommended annually for all sexually active people. Those with new or multiple partners should test every 3 months. Testing is free at NHS sexual health clinics and from online services (SH:24, SHGM). You do not need symptoms to be tested — most STIs cause no symptoms. A full STI screen covers chlamydia, gonorrhoea, syphilis, HIV, hepatitis B, and hepatitis C. Specific sites tested (urine, swabs, blood) depend on your sexual practices. Results are usually available within 1–2 weeks. Positive results trigger automatic partner notification advice.
Not all STIs are curable, but all are treatable. Bacterial STIs — chlamydia, gonorrhoea, and syphilis — are fully curable with antibiotics when diagnosed promptly. Viral STIs — HIV, herpes, HPV, and hepatitis B — cannot be cured but can be effectively managed. HIV is controlled with ART to the point of undetectability. Herpes is managed with antivirals that suppress outbreaks. HPV often clears naturally within 1–2 years in people with healthy immune systems. Genital warts can be treated and removed, though the underlying HPV virus may persist. The key message: all STIs are manageable with prompt diagnosis and treatment.
Yes. HIV is now a manageable chronic condition, not a death sentence. With antiretroviral therapy (ART), people with HIV can live long, healthy lives with a normal life expectancy. ART suppresses the virus to undetectable levels in the blood, meaning it cannot be transmitted sexually (Undetectable = Untransmittable, or U=U). Most people on modern ART take a single tablet daily and experience minimal side effects. HIV does not prevent you from having children, working, or having a fulfilling life. In the UK, HIV care is excellent and free on the NHS. The biggest barrier to good outcomes is late diagnosis — testing early is life-saving.
PEP (post-exposure prophylaxis) is a 28-day course of antiretroviral drugs that prevents HIV infection after a potential exposure. It must be started within 72 hours — the sooner the better. PEP is available from A&E departments, sexual health clinics, and some GUM clinics 24/7. It is free on the NHS for NHS patients. PEP is not a substitute for PrEP or condoms and should be used only in genuine emergencies (unprotected sex with a known HIV-positive person not on suppressive ART, condom failure, sexual assault, or needlestick). After completing PEP, an HIV test at 45 days and 3 months confirms whether infection was prevented.
Yes, but safely. With modern antiviral suppression, the risk of transmitting herpes to a partner is substantially reduced. Daily suppressive valaciclovir reduces transmission risk by approximately 50%, combined with condom use. Disclosing herpes to a new partner is an important conversation — most people with herpes have had it from a previous partner without knowing. Your sexual health clinician can help with disclosure conversations and partner testing. Most people with herpes continue to have satisfying, loving relationships. Herpes is extremely common — HSV-2 affects around 1 in 6 adults — and carries significant social stigma disproportionate to its medical impact.
Without treatment, chlamydia can persist silently for months or years, causing progressive damage to the reproductive tract. In women, untreated chlamydia causes pelvic inflammatory disease (PID) in 10–15% of cases, leading to tubal factor infertility, chronic pelvic pain, and ectopic pregnancy risk increased 6–10-fold. In men, chlamydia causes epididymo-orchitis, which can impair sperm production and quality. Reactive arthritis (formerly Reiter's syndrome) — involving joint inflammation, eye inflammation, and urethritis — is a rare but recognised complication. These complications are entirely preventable with prompt diagnosis and a simple 7-day course of doxycycline.
Gonorrhoea is increasingly difficult to treat due to rising antibiotic resistance. The current UK first-line treatment is a single intramuscular injection of ceftriaxone 1g. A test of cure is required 2 weeks later to confirm eradication. Azithromycin is no longer recommended routinely due to resistance. Multidrug-resistant gonorrhoea has been identified in multiple countries, including the UK. If you have been treated for gonorrhoea and symptoms persist, return to the clinic immediately — do not take additional antibiotics without guidance. Treatment of all recent sexual partners is essential to prevent reinfection.