What Is Syphilis?

  • Grace Russell PHD Researcher at University of the West of England
  • Ellen Rogers MSc in Advanced Biological Sciences, University of Exeter, UK

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Syphilis is a sexually transmitted infection (STI) caused by a bacterium called Treponema pallidum. It can be a serious infection and lead to severe health problems if left untreated. Syphilis is primarily transmitted through sexual contact, including vaginal, anal, and oral sex. However, the infection can also be passed from mother to child during pregnancy or delivery. Syphilis is not spread through casual contact, such as shaking hands or sharing eating utensils.

Syphilis has been a significant disease for centuries. The first recorded outbreak of syphilis occurred among French troops besieging Naples in 1494.1 After this outbreak, the disease quickly spread throughout Europe and was dubbed the "Great Pox." It was not until the discovery and introduction of penicillin in the 1940s that a reliable cure for syphilis was found.

Syphilis is primarily transmitted through sexual contact. Infected individuals are often at increased risk of HIV infection, whilst mothers with syphilis can pass the infection to their babies, putting them at risk of serious health problems. Testing for syphilis typically involves a blood test, and treatment involves antibiotics. Preventative methods include practising safe sex, regular STI testing, and treating infected individuals and their partners. 

Causes of syphilis infection

Syphilis is caused by a bacterium called Treponema pallidum and is transmitted mainly through sexual contact. Syphilis is a highly contagious infection and can be easily spread through sexual contact with an infected individual - including individuals who are asymptomatic or unaware of their infection. Syphilis can also be transmitted by sharing needles or other equipment used for injecting drugs. The bacteria can also enter the body through tiny cuts or abrasions in the skin or mucous membranes and can also be passed from mother to child during pregnancy or delivery. It is important to note that syphilis cannot be contracted through casual contact, such as sharing utensils, toilet seats, or clothing. It is also not spread through kissing or hugging.

Syphilis infection manifests in three stages: primary, secondary, and tertiary syphilis. Each of these stages has its own distinct symptoms and complications. Primary syphilis is characterised by the appearance of a painless sore (or chancre). Secondary syphilis is marked by a rash, fever, sore throat, muscle aches, and fatigue. Tertiary syphilis only occurs when the infection has progressed to a late stage and can cause severe health problems, including damage to the brain, nerves, eyes, heart, blood vessels, liver, bones, and joints. These stages are discussed in further detail in the next section of this article.

Factors increasing your risk of contracting syphilis include having unprotected sex with multiple partners, having sex with a partner who has (or has had) multiple sexual partners, and having sex with someone who has had sexually transmitted infections in the past.

Signs and symptoms of syphilis infection

Syphilis has also been called “The Great Pretender” or “The French Disease”, as its characteristic symptoms can resemble those of other diseases.2,3 However, syphilis typically progresses in stages over weeks, months, or even years.

Stage 1: Primary syphilis

Usually, the first sign of syphilis infection is a painless sore (or chancre) at the site of infection (usually the genitals, anus, or mouth). The sore typically appears within three weeks of exposure and can last for several weeks. It may go unnoticed, especially if it is inside the body, and can easily be mistaken for a harmless bump or lump.

Stage 2: Secondary syphilis

If left untreated, syphilis progresses to the secondary stage. This stage is characterised by a rash that can appear anywhere on the body, including the palms of the hands and the soles of the feet. Besides this rash, secondary syphilis can cause fever, sore throat, muscle aches, fatigue, and swollen lymph nodes. The rash can last for several weeks or months, be red or brown in colour, and even feel rough or scaly. If you think you may have these symptoms, it is important to contact your doctor, as syphilis is highly contagious at this stage.

Stage 3: Tertiary syphilis

If syphilis is still left untreated, it can progress to the tertiary stage - the most severe stage of the infection. Tertiary syphilis can cause a wide range of complications, including damage to the brain, nerves, eyes, heart, blood vessels, liver, bones, and joints.4 Other possible symptoms of tertiary syphilis include paralysis, dementia, blindness, deafness, and severe organ damage.

Other signs and symptoms

In addition to the above-mentioned signs and symptoms, syphilis can also cause other health problems, such as swollen lymph nodes, weight loss, and hair loss. The infection can also increase the risk of HIV infection.

Management and treatment for syphilis infection

The management and treatment of syphilis involves a combination of medication, lifestyle changes, and regular follow-up care. If you or your partner have syphilis, it is very important to be aware of disease control measures and how to prevent the transmission of the infection.

It can take up to 3 weeks or more for the symptoms of syphilis to appear after you have been infected. Sometimes, the symptoms can improve by themselves, but the infection will still be in your body until you are treated. This means that you can still pass it on to others, and you remain at risk of further health issues.

You should visit a sexual health clinic or see your GP if:

  • You or a sexual partner have symptoms of syphilis, or a partner has told you they have syphilis (or another sexually transmitted infection)
  • You have recently had sex with a new partner and did not use a condom 
  • You are pregnant or planning to get pregnant and think you might have syphilis
  • You used a needle to inject drugs that have been used by someone who might have syphilis

The only way to confirm if you have syphilis is by having a blood test. Your doctor or nurse may have to examine you for evidence of sores or rashes. If you do test positive, treatment will need to be started as soon as possible.

Medication for syphilis

The primary treatment for syphilis is antibiotics, which kill the bacteria which cause it.5 The type of antibiotic used depends on both the stage and severity of your infection. Penicillin is the most commonly used antibiotic for the treatment of syphilis, but other antibiotics may be used if you are allergic to it. 

The duration of treatment will vary depending on the stage of the infection. Generally, early-stage syphilis requires a shorter course of treatment than late-stage syphilis. It is important to take all the medication as prescribed to ensure that the infection is fully treated and to prevent the development of complications, even if your symptoms improve or disappear early on.

Lifestyle changes

In addition to medication, lifestyle changes can also help manage syphilis and prevent the spread of the infection. This includes practising safe sex (for example, using condoms and dental dams), avoiding sex toys that are shared with others, and getting tested regularly. It is also important to notify sexual partners about the infection and encourage them to get tested and treated.

Follow-up care

After treatment for syphilis, it is important to receive regular follow-up care to monitor for any complications or recurrence of the infection. This involves regular blood tests to check for the presence of the bacteria, as well as physical exams, to check for any signs of complications, such as damage to the heart or nervous system.

Disease control measures

Disease control measures are also important in preventing the spread of syphilis. This involves contact tracing and partner notification - identifying and treating all sexual partners of infected individuals to prevent further transmission of the disease.


There is currently no vaccine for syphilis. However, to help prevent the spread of syphilis, the following has been advised:

  • Abstain from sex, or be monogamous (have one partner). The only certain way to avoid syphilis is to avoid having sex; however, practising monogamy can help keep both of you safe.
  • Use condoms. Condoms reduce your risk of contracting syphilis, but only if they cover any sores.
  • Avoid recreational drugs. Misusing alcohol or drugs and sharing needles with other users can inhibit your judgment and may put you at risk of contracting syphilis or other infections.


Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum. Syphilis infection can be contracted via sexual contact with infected individuals and follows three distinct stages: primary, secondary, and tertiary. 

Syphilis can be easily treated with antibiotics, but if left untreated, it can lead to serious health problems and even death. It is important to get tested regularly for STIs, including syphilis - especially if you are sexually active with multiple partners. Safer sex practices, such as using condoms, can also help prevent the spread of syphilis and other STIs.


What are the stages of syphilis infection?

Syphilis infection progresses through three stages: primary, secondary, and tertiary syphilis. The primary stage is characterised by a painless sore called a chancre at the site of infection. Secondary syphilis involves a rash and flu-like symptoms, while tertiary syphilis can cause severe complications such as neurosyphilis, cardiovascular syphilis, and gummas.

How is syphilis infection diagnosed?

Syphilis infection is diagnosed through blood tests. These tests detect antibodies to the bacterium that causes syphilis, Treponema pallidum. A physical exam and a review of symptoms are also important in making a diagnosis.

How can I prevent syphilis infection?

Syphilis infection can be prevented by practising safe sex, getting tested regularly for sexually transmitted infections, and limiting sexual partners. It is also important to avoid sharing sex toys and to undergo treatment for syphilis if diagnosed.

Who is at risk of syphilis infection?

Anyone who is sexually active is at risk of syphilis infection, but people who engage in unprotected sex or have multiple sexual partners are at a higher risk. Pregnant mothers with syphilis can also transmit the infection to their unborn child.

How common is syphilis infection?

According to the Centers for Disease Control and Prevention (CDC), syphilis is the third most commonly reported notifiable disease in the United States. In 2019, there were over 129,000 cases of syphilis reported, with the highest rates being seen in people assigned male at birth who have sex with people assigned male at birth and people assigned female at birth of reproductive age.

Is syphilis contagious?

Yes, syphilis is contagious and can be transmitted through sexual contact with someone who has an active infection. It can also be transmitted from an infected mother to her unborn child.

When should I see a doctor?

If you have symptoms of syphilis or have had sexual contact with someone who has syphilis, you should see a doctor for testing and evaluation. It is important to get treatment as soon as possible to prevent the spread of the infection and to avoid complications of untreated syphilis.


  1. Fenton KA, Breban R, Vardavas R, Okano JT, Martin T, Aral S, et al. Infectious syphilis in high-income settings in the 21st century. Lancet. Infect. Dis. 2008;8(4):244-53.
  2. Cahalan S. The great pretender: The undercover mission that changed our understanding of madness. New York: Grand Central Publishing; 2019.
  3. Plagens-Rotman K, Jarząbek-Bielecka G, Merks P, Kędzia W, Czarnecka-Operacz M. Syphilis: then and now. Postepy. Dermatol. Alergol. 2021;38:550-4.
  4. Hook EW. Syphilis. Lancet. 2017 [cited 2023 Mar 8];389:1550-7. Available from: https://doi.org/10.1016/S0140-6736(17)31290-4
  5. Clement ME, Okeke NL, Hicks CB. Treatment of syphilis: a systematic review. Jama. 2014;312:1905-17.

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