Syphilis is a sexually transmitted infection (STI) caused by a bacterium (bug) called Treponema pallidum. It enters the body through tiny breaks in the skin, mainly in the genital area or the mouth.

Key points

  1. Syphilis is very infectious and is usually caught by having close sexual contact with an infected person.
  2. Many people do not get any symptoms and would not know they had syphilis without having a blood test.
  3. Syphilis testing is included in routine sexual health checks.
  4. Treatment is normally with injections of an antibiotic called penicillin.
  5. If left untreated, the syphilis bacteria eventually causes damage to the internal organs. People without symptoms can still develop these problems later on if not treated.
  6. Syphilis has multiple possible symptoms, many of which are very similar to other diseases, because of this, syphilis is also known as 'the great imitator'. 


How do you get syphilis?

Syphilis is very infectious and is usually caught by having close sexual contact with an infected person. This may include vaginal, anal or oral sex or just close skin-to-skin contact. The chances of catching syphilis are lower if you use condoms during sex. Syphilis can also be spread from mother to baby during pregnancy if the mother is infected. It can cause miscarriage or still-birth.

Syphilis is highly infectious in the earlier stages, so it is important to diagnose and treat it as soon as possible to prevent its spread.

What is the link between syphilis and HIV?

It is now known that the genital sores caused by syphilis in adults also make it easier to transmit and acquire HIV (human immunodeficiency virus) infection sexually. There is a two to five times greater risk of catching HIV infection when syphilis is present.


Many people do not get any symptoms and would not know without having a blood test.

For those who do get symptoms, syphilis is divided into three stages: primary, secondary and tertiary.

  • Primary and secondary syphilis are also known as infectious syphilis.
  • Tertiary syphilis is known as non-infectious or late-latent syphilis. 

Primary syphilis

The first sign of syphilis is a sore, usually on the genitals but it may be at other sites of sexual contact. The sore may occur in hidden sites (e.g. cervix, mouth, anus) and because it is usually painless it may go unnoticed. It usually appears three to four weeks after infection, but sometimes it takes longer. The sore will disappear on its own accord within a few weeks. 

  • Even though the sore heals, you still have the syphilis infection and can pass it onto others.
  • Any genital sore must be examined by a doctor, even if it starts to heal and it is small and painless. 

Secondary syphilis

Later on, sometimes a rash will appear quite suddenly about six weeks after infection. It may appear on the body, face, arms and often on the palms and soles of the feet. The type and extent of the rash will vary from person to person and even vary on different parts of the body of the same person. It may be very obvious but it may be so mild as to pass unnoticed, and often disappears as suddenly as it appeared. The rash lasts up to four to six weeks.

There may also be one or more of the following symptoms: 

A person in primary or secondary stage of syphilis is very infectious because the sores and rashes are full of syphilis bacteria. There is a very high chance of infecting a sexual partner.

If syphilis is not treated in the primary or secondary stage the symptoms will disappear. After two years the person is usually not infectious to others. At this stage, infection is only picked up on blood tests.

Tertiary syphilis

In about a third of people, if not treated, the syphilis bacteria will eventually cause damage to the internal organs. These include the heart, brain and the nerves in the spinal cord. The doctor may advise that a chest x-ray or a lumbar puncture (spinal tap) is needed to help assess if any of these parts of the body are affected.

Treatment is still effective and can prevent further damage, but will not repair any damage that has already taken place. Tertiary syphilis is not infectious and can be avoided by treatment at an earlier stage.

How is syphilis diagnosed?

Syphilis is usually diagnosed by blood tests for antibodies to the syphilis bacterium, these should be part of any sexual health check. Ask your doctor or nurse if you can be tested for syphilis when having a check-up. It can take up to three months to develop antibodies, so the tests may be negative early on. If you have a genital sore or body rash, the doctor may need to take samples from the sores, to be sent for laboratory analysis. The doctor will also order blood tests to detect syphilis infection.

Does syphilis affect pregnancy?

Depending on how long a pregnant woman has been infected, she has a good chance of passing the infection to her unborn baby and this could result in stillbirth or miscarriage. An infected baby may be born without symptoms but could develop them within a few weeks. The baby could become very ill. 

It is recommended that every woman should have a blood test for syphilis during pregnancy. Proper treatment of the mother during pregnancy will prevent the baby being born with syphilis. 

What about sexual partners?

If you have been diagnosed with syphilis all your sexual partners from the last few months must be advised to attend their doctor or local clinic. 

  • If you had sex with them while the rash or sore was present they will usually need treatment.
  • You should not have sex until your rash or sore clears up because you remain infectious for some time after treatment. This is the only way to control the disease and protect the health of sexual partners.
  • Anyone who has had sex with an infected person in the past must be tested and treated if necessary.
  • Some people feel embarrassed, scared or angry when they or their partner has a sexually transmitted infection (STI). This is common and okay. Do not let these feelings stop you from getting medical help or telling your partner. Anyone who is sexually active can get an STI.
  • Talk to partners as soon as possible. If left untreated, syphilis can cause complications and be spread to other partners. Tell current partners or past sexual contacts to see their doctor or sexual health clinic because they may have an STI.
  • If you need help contacting your partner(s), talk to the doctor or nurse at the sexual health clinic for advice. 


The length of treatment varies according to the stage of infection and type of antibiotic used. In most cases penicillin injections are used but under certain circumstances the medication may be taken by mouth (e.g. tetracycline or erythromycin tablets). Take the treatment exactly as prescribed and do not miss any doses, as this will reduce its effect. 

After treatment with penicillin injections some people (particularly in early syphilis) have a flu-like illness for 24 hours. This includes fevers, aches and pains, and generally feeling unwell. This will go away and doesn't require any special treatment, except possibly over-the-counter medication (such as paracetamol) for fever and pain, and having adequate rest. 

After treatment, follow-up blood tests are essential for at least one year to ensure the treatment has been successful. 

If it seems likely that the infection has occurred recently, sexual partners are also usually treated because the blood tests may not become positive for several weeks.

Should I avoid sex when I have syphilis?

You should not have sex until your rash or sore clears up because you remain infectious for some time after treatment. How long will vary from one person to another so it is a good idea to ask if your doctor or nurse has not discussed this with you. This is the only way to control the disease and protect the health of sexual partners.

How is syphilis prevented?

The only sure way to avoid getting syphilis or other STIs is not to have sexual contact. If you do decide to have sexual contact, you can reduce your risk by: 

  • Having sex with one person who has sex only with you.
  • Using condoms until you and your sexual partner(s) have been checked for STIs.
  • Having regular sexual health check-ups. 

Where do I go for a check-up?

Sexual health clinics have specialists who are experienced in the management and diagnosis of syphilis. Treatment is free and confidential and the people there can help with testing your sexual partners or family members. 

Learn more

What is syphilis? Auckland Sexual Health Service, 2015
Syphilis 'back with a vengeance' Fairfax NZ Limited, 2014
Syphilis U.S Department of Health and Human Services and National Institute of Allergies and Infectious Diseases, 2014
Syphilis resources Centres for Disease Control and Prevention, USA, 2014

Credits: Editorial team.