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What Is Syphilis?

Syphilis is an infection caused by a type of spiral shaped bacterium called Treponema pallidum. It’s transmitted almost exclusively through close, direct contact — most often during unprotected vaginal, anal, or oral sex with someone who already has the infection. Because the initial symptoms can be very mild or even go unnoticed, many people don’t realize they have syphilis until weeks or months later, when more obvious signs appear.

Although it’s most commonly thought of as a “sexually transmitted disease,” syphilis can also be passed from an untreated pregnant person to their baby, potentially leading to serious complications, or even stillbirth. The bacterium burrows into the body through tiny breaks in the skin or mucous membranes, then spreads through the bloodstream. If it isn’t treated promptly, syphilis can progress through several stages (primary, secondary, latent and tertiary), causing anything from painless sores and rashes in its early phases to potentially life-threatening damage to the heart, brain, nerves and other organs in its later stages.

Despite its seriousness, syphilis is entirely curable — especially when caught early. A single injection of a long-acting penicillin antibiotic can wipe out the infection in most cases, and follow-up blood tests ensure that treatment has been successful. Because untreated syphilis raises the risk of passing on HIV and can lead to irreversible harm over time, regular testing (especially if you have new or multiple partners) and honest conversations with sexual partners and healthcare providers are the best defences against this once common, now resurgent infection.

Professional GP advice, anytime, anywhere

What Causes Syphilis?

Bacterial origin: Treponema pallidum is a spiral-shaped bacterium that penetrates mucous membranes or tiny breaks in the skin.
No animal reservoir: Humans are the only natural host; the infection cannot be acquired from animals.
Incubation period: Symptoms typically appear 10–90 days after exposure, with an average of around three weeks.

How Is Syphilis Transmitted?

Sexual contact: Vaginal, anal or oral sex without barrier protection can transfer the bacterium via direct contact with an infectious lesion (chancre).
Vertical transmission: An untreated pregnant person can pass syphilis to their fetus, leading to congenital syphilis with risks of miscarriage, stillbirth or severe neonatal disease.
Rare routes: Blood transfusion or accidental needle sticks (now very uncommon in the UK thanks to rigorous screening).

The Stages and Symptoms

Syphilis often unfolds in four overlapping stages. Early stage lesions may be so subtle that many people do not seek care until secondary signs (like a rash) appear.

Diagnosis and Testing

Clinical examination: Visual inspection and history-taking at a sexual health clinic or GP.
Serologic tests: Blood tests detect antibodies to T. pallidum. May include non-treponemal tests (e.g., VDRL) followed by treponemal confirmatory assays.
Lesion swabs: In primary syphilis, swabbing the chancre for direct detection of the bacterium can confirm diagnosis more rapidly.

Treatment Options

Syphilis is curable with appropriate antibiotic therapy:

First-line: Intramuscular benzathine penicillin G.
Alternatives: Oral doxycycline or tetracycline for penicillin-allergic individuals (with careful follow-up).
Follow-up: Serial blood tests at 6 and 12 months post-treatment to ensure serologic response.

Early treatment not only cures the infection but also prevents long-term complications.

Prevention and Protection

Barrier methods: Consistent and correct use of condoms or dental dams significantly reduces risk.
Regular testing: Especially if you have new or multiple partners, or if a partner tests positive for any STI.
Partner notification: Informing recent sexual partners so they can get tested and treated is vital for breaking transmission chains.
Antenatal screening: All pregnant people in the UK are offered syphilis testing early in pregnancy to prevent congenital infection.

Recent Trends in the UK

After decades of decline, syphilis cases have surged in England and Wales, reaching levels not seen since the mid-20th century:

Council-area data: Syphilis diagnoses increased by 71% across almost every local authority between 2017 and 2022 The Guardian.
Healthcare impact: Hospital admissions for treatable STIs including syphilis, have risen sharply amid funding cuts to sexual health services, further stressing the need for awareness and early care The Guardian.

When to Seek Help

You notice a painless sore on your genitals, mouth or anus.
You develop an unexplained rash, especially on your palms or soles.
A sexual partner notifies you of an STI diagnosis.
You’re pregnant or planning pregnancy and haven’t been tested recently.

If any apply, contact your local sexual health clinic or GP promptly, early diagnosis and treatment are key.

Conclusion: Syphilis remains a significant public health concern, but it is both detectable and treatable when managed early. Regular testing, safer-sex practices and timely treatment not only protect individual health but also curb further transmission. Stay informed, stay tested, and talk openly with partners and healthcare providers to keep syphilis and other STIs under control.