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Syphilis Infection

Written by Ada’s Medical Knowledge Team

Updated on

What is syphilis?

Syphilis is a common sexually transmitted infection caused by a bacterial infection, this infectious organism is known as Treponema pallidum.

There are 2 general types of infection: acquired syphilis and congenital syphilis (when an infected mother transmits the infection to the baby during pregnancy). Overall, young adults are the group most commonly affected by syphilis.

The early symptoms are small, painless sores on the genitals and enlarged lymph nodes in the neck or groin. This condition can affect many different parts of the body, so later, symptoms can differ widely from person to person. Practising safe sex using condoms helps to reduce the risk of catching syphilis. Antibiotics are used to treat the infection, with early and effective treatment, most people recover well.

Causes and risk factors of syphilis

Syphilis is a sexually transmitted infection caused by a microorganism called Treponema pallidum. 1 Syphilis infection is most commonly found in young adults aged 25-29 years. 2 Certain factors can increase the risk of contracting a syphilis infection, these can include: 3 4

  • Practising unsafe sex such as not using condoms
  • Having multiple sexual partners
  • Having sex with an infected partner
  • Being infected with HIV or another STI
  • Born to a mother who has been infected with syphilis during pregnancy; leading to congenital syphilis
  • Illicit drug use (sharing needles)

Oral sex is also an important route of transmitting Treponema pallidum where the transmission can occur despite the use of condoms. 1 In addition, men who have sex with men (MSM) are also at higher risk of contracting a syphilis infection, particularly if they're also co-infected with HIV. In 2019, approximately 56.7% of all reported primary syphilis and secondary syphilis cases in the US occurred in MSM. 5

What syphilis stages exist?

Acquired syphilis has 4 stages: primary, secondary, latent and tertiary: 1 4 6

Primary syphilis is the initial stage of infection. In this stage, a flat, painless ulcer known as a chancre develops at the point where the infection entered the body. The chancre usually appears between 10 and 90 days after infection and heals on its own after about 3 to 12 weeks. The chancre will heal whether or not the affected person receives treatment. However, unless the infection is treated, the affected person remains infectious even once the chancre has healed.

Secondary syphilis develops around 4-8 weeks after a primary syphilis infection, however, symptoms can occur up to 6 months after a primary infection. Secondary syphilis can develop in individuals who are not treated for primary syphilis. Symptoms can include a widespread rash, swollen lymph nodes and involvement of other organs, which is less common.

Latent syphilis is the presence of Treponema pallidum bacteria without any symptoms of primary, secondary or tertiary infection. 7 Latent syphilis comes in 2 forms: 1 4 6 7 8

  • Early latent syphilis: infection occurs within the past 12 months; around 25% of patients experience a relapse of secondary syphilis
  • Late latent syphilis: infection occurs more than 12 months ago; no relapse and not infectious

Tertiary syphilis can occur years to decades after initial infection and can have life-threatening complications with organ involvement. Any organ can be involved such as the nerves, ears and eyes, but the 3 main forms of tertiary syphilis include: 1 4 7 8

  • Benign tertiary syphilis (also known as Gummatous syphilis): a rare complication where soft rubbery lesions, also known as gummas form on the skin, and organs, particularly the liver and bones. They can break down and form a sore, and if untreated, can destroy surrounding tissues. Bone involvement can cause excruciating pain. Gummatous syphilis can be treated with IV Penicillin. 9
  • Cardiovascular syphilis; the bacteria infect the heart and blood vessels and can present in the form of aortitis (inflamed aorta), aneurysms, and signs and symptoms of heart failure which can be life-threatening.
  • Neurosyphilis is a form of syphilis that affects the brain, the membranes covering the brain, and the spinal cord. Although it's most often associated with the tertiary stage of syphilis, it can occur at any stage of the condition. 10

What is congenital syphilis?

It's also possible for pregnant people who have contracted syphilis during pregnancy to pass on the infection to their children in utero, meaning in the womb, this type of infection from mother to child can be called Congenital syphilis. 8 11 Complications of congenital syphilis include: 11 12

  • Miscarriage
  • Stillbirth
  • Prematurity
  • Low birth weight
  • Death shortly after birth

It's important to note that untreated congenital syphilis contains a high risk of stillbirth and death due to infection as a newborn. Babies born with congenital syphilis can experience skin rashes, meningitis, neurological problems such as blindness or deafness, jaundice (yellowing of the eyes or skin), enlarged liver or spleen, anaemia, and bone deformities. 11

Manifestations after birth are categorized into 2 stages: early and late congenital syphilis. Early congenital syphilis is when manifestations can occur within the first 2 years of age and late-stage manifestations occur after 2 years. 13

Clinical signs may not be present at birth, this can take up to 3 months to develop. It's recommended that all pregnant women should be tested for syphilis during the first antenatal care visit. 11 If tested positive for syphilis, treatment should be started right away to reduce the risk of transmission to the baby. 11

Syphilis symptoms: What does syphilis look like?

There are 2 major symptoms that strongly suggest a primary syphilis infection. They heal spontaneously therefore may not always be noticed. These symptoms are: 4 8 13

  • a painless ulcer (also known as a chancre) in the genital region, mouth or buttocks
  • painless, rubbery swollen lymph nodes

Sometimes ulcers may be painful and multiple in numbers. Medical research suggests that a co-infection with Herpes or Chancroid may be the cause. Multiple syphilis ulcers may also be found in a co-infection with HIV 13.

If you are concerned that you may have contracted an infection, you can do a free symptom assessment using the Ada app at any time.

Secondary syphilis symptoms may arise 4-8 weeks after, and up to 6-months following a primary infection. Non-specific symptoms can include fever, muscle pain, joint pain, fatigue and malaise (sense of discomfort and becoming ill, or lack of well-being). There may also be: 13

  • More widespread swollen lymph nodes
  • Rash in the palms, inner soles of the feet, trunk or scalp (the rash may be in the form of a papule (small raised bumps on the skin) which can become an ulcer)
  • Ulcer in the inside of the mouth
  • Wart-like lesions in the genital area (known as condylomata lata)
  • Patchy hair loss
  • Organ involvement – uncommon

Latent syphilis does not show any signs or symptoms; this can be referred to as asymptomatic.

**Tertiary syphilis symptoms are characterised by end-organ complications which often occur many years after infection. These include: 4 8 10 13

  • Benign tertiary syphilis: chronic skin ulceration and organ involvement; causing enlargement of organs (organomegaly), infective or destructive lesions (gummatous lesions) – a rare form of tertiary syphilis
  • Cardiovascular syphilis: chest pain and difficulty breathing – a cardiology consultation is advised.
  • Neurosyphilis, although most associated with tertiary syphilis can occur at any stage of a syphilis infection. A variety of neurological problems can arise and symptoms can include: 13

Headache, loss of hearing, meningismus (headache, neck stiffness, photophobia – being sensitive to light along with nausea and vomiting), vision problems, damage to the spinal cord, behavioural changes, memory impairment, seizures, tremors, loss of reflexes

Congenital syphilis symptoms after birth are categorised into 2 different stages: early congenital syphilis and late congenital syphilis. Symptoms of early congenital syphilis include: 14

  • Large blisters
  • Copper-coloured rash on palms of hands
  • Papules (raised bumps) around the nose, mouth and diaper area
  • General swelling of lymph nodes
  • Enlargement of the spleen and liver
  • Runny nose – discharge can be bloody

Inflammation of the bones and cartilage can be found in early congenital syphilis, this can cause bones to develop improperly and restrict movement of the infant.

In late congenital syphilis, symptoms are seen after 2 years of life, infants can present with: 14

  • Ulcers (sores) in the mouth
  • Abnormal development of bones (affecting the shins, face)
  • Problems with development of the teeth
  • Blindness or scarring of the eye
  • Hearing loss – can occur at any age

Diagnosis syphilis

The diagnosis of syphilis is usually made based on the symptoms, a physical examination and a blood test for syphilis antibodies, which are proteins that fight the infection. Testing for syphilis antibody is also known as serology. Serology testing for syphilis is usually done on blood samples, 2 types of tests that are used in diagnosis are: 4 8 13

  • Treponemal tests: detect specific antibodies to Treponema pallidum
  • Non-treponemal tests: non-specific, test for antigens produced by a syphilis infection, not specifically for the Treponema pallidum microorganism itself. This acts more as a screening tool.
  • At-home syphilis tests are also available, where a blood sample can be collected from a finger prick

Non-treponemal tests can produce false results, therefore a treponemal test is carried out initially, followed by a non-treponemal test to confirm the diagnosis. This is more time and cost effective. ref8

In primary and secondary syphilis, diagnosis can also be made by using darkfield microscopy. ref4 ref8 ref13 This is when a sample of fluid is collected from the syphilis sore or swollen lymph node, and examined under a special microscope. For latent syphilis, serology testing can be carried out.

Diagnosis of tertiary stage syphilis relies on clinical symptoms and blood test results. In the case of suspected neurosyphilis; a lumbar puncture (LP) may be needed. ref13 A lumbar puncture is when fluid is collected from the spine, for diagnostic purposes.

For early congenital syphilis can be done during a routine blood test during pregnancy, this test is usually repeated during the 3rd-trimester and at delivery. The collected samples are examined by microscopy.Collected samples include: ref14

  • Blood sample from the mother
  • Sample from the placenta
  • Sample from the umbilical cord
  • Lesion during active infection of the mother

During active infection of the mother, a physical examination may be carried out by the doctor to look for symptoms and manifestations. It is advised that children who show signs, symptoms and a positive blood test should undergo a lumbar puncture, to investigate the involvement of the brain.

Physicians can make a diagnosis of late congenital syphilis in the presence of specific symptoms that are associated with it along with a positive blood test. ref13 ref14 An X-ray may also be required in the presence of bone deformities in children.

Syphilis treatment

The treatment of syphilis is with appropriate antibiotics. 15 An injection of Benzathine penicillin G is the first line treatment according to the CDC for a syphilis infection. 15 16 The form of administration of the medication, dosage, and length of treatment are determined by the stage and clinical manifestations. Current recommendations are: 15 16

  • Primary, secondary or early latent syphilis: single-dose long acting Benzathine penicillin G
  • Latent syphilis: 3 doses of long-acting Benzathine penicillin G at weekly intervals

It is important to remember that if you are allergic to penicillin, alternative antibiotic medication can be prescribed. The most commonly used alternative is Doxycycline.

Within 24 hours of starting antibiotic therapy, some patients can experience an illness with fever, headache and muscle pain, this is known as a Jarisch-Herxheimer reaction. 17 Corticosteroid therapy may be considered to minimize the risk of Jarisch-Herxheimer reaction. 17

Syphilis Prevention

There are certain measures which you can take to prevent being infected with syphilis as well as passing it onto others. These include: 18

  • Use condoms when having vaginal, anal or oral sex
  • Make sure to complete your treatment regimen if you are taking medication for a syphilis infection
  • Do not share adult toys
  • Do not share needles

Syphilis FAQs

Q: Is syphilis contagious?
A: Yes. Syphilis can be passed from person to person. Most people contract syphilis through sexual contact with an infected person, but it is also possible for mothers with syphilis to pass the infection on to their children during pregnancy. Rarely, people who share injection apparatus or who are pricked by a contaminated hypodermic needle may contract syphilis if the needle has been used by someone with syphilis.

Q: Who should be tested for syphilis?
A: Those who should seek testing for syphilis include:

  • Any asymptomatic person who is concerned that they may have been exposed to syphilis by a sexual or intimate partner
  • Anyone showing any symptoms of any stage of syphilis
  • All pregnant women or women who are planning to become pregnant
  • Anyone who has recently had unprotected sex with a new partner whose STI status they do not know
  • Anyone who has recently had unprotected sex with multiple partners
  • Anyone who has another STI, such as chlamydia or gonorrhea, or whose partner has disclosed that they have an STI
  • Anyone who is HIV-positive
  • Men who have sex with men
  • Anyone who has previously had syphilis

Q: What should I do if I think I have syphilis?
A: Anyone who suspects that they may have syphilis should go to a doctor, clinic or specialized sexual health clinic and ask to be tested for syphilis.

Q: Should people who do not show symptoms but think they may have been exposed to syphilis seek testing for syphilis?
A: Yes. It is possible for syphilis to be asymptomatic. If you think you have been exposed to syphilis by an intimate or sexual partner, but do not show symptoms, you should seek testing. It is especially important to seek testing if you may fall pregnant, engaged in unprotected sex, and/or have multiple sexual partners.

Q: Are people who have unprotected sex at risk of contracting syphilis?
A: Yes. Syphilis is spread by sexual activity, such as oral sex, anal sex and vaginal sex, as well as any other genital contact and sharing of sex toys. Syphilis is transmitted by direct contact with a chancre during sex.

Q: Can one contract syphilis through sharing sex toys?
A: Yes, if one’s sexual partner has syphilis, and sex toys are shared between partners.