What is syphilis?

Updated on:
June 28, 2021

Syphilis is a sexually transmitted infection caused by the bacteria Treponema (T) pallidum. It is passed through sexual contact with a person who’s infected, pregnancy, childbirth, and sharing drug equipment. The infection can be present around the genitals, and inside the rectum and mouth.

Although most people present no symptoms, syphilis can be detected through STI tests and is an easily treatable infection.

The different types of syphilis

There are three types of symptomatic syphilis, which refer to the progression of untreated infection: primary, secondary, and tertiary (late) syphilis. Neurologic syphilis (early or late) and congenital syphilis (passed through pregnancy), are unfortunate, yet uncommon, complications. The latent (i.e. asymptomatic) stages are either early, within the first year of infection while still infectious, or late, after the first year when not infectious to others (unable to transmit).

Primary syphilis refers to the early stages of the bacterial infection, where a lesion (sore) can appear around the genitals or mouth, usually within two to three weeks after infection. Lymph-nodes in the groin or neck may also become swollen. Early stage syphilis can also have no symptoms and go unnoticed, highlighting the importance of regular STI testing for sexually active people.

Secondary syphilis, in general, represents weeks 2-12 after the appearance of a lesion. At this point, the body may start showing signs of generalized infection, such as: rash, fever, low-energy and appetite, sore throat, and lesions.

Early neurosyphilis involves central nervous system infection (brain and spinal cord), which may happen with or without symptoms. Some symptoms of nervous system impact can include: ringing in the ears, decreased hearing and seeing ability, headaches.

Tertiary (late) syphilisis the result of undetected and untreated syphilis. This stage is asymptomatic and can develop 2-30 years after infection. Late syphilis can impact any organ system in the body and cause it to slowly become inflamed. If untreated, late-stage syphilis can lead to numerous health impacts: difficulty falling asleep, vision problems, changes in personality, poor memory, meningitis, seizures, etc. In rare cases, it can be life-threatening.

Late neurosyphilis results in irreversible central (brain) or peripheral (body) nerve damage including memory loss, dementia, psychosis, pain, weakness, and balance issues.

Congenital syphilisis when a parent with syphilis gets pregnant and/or gives birth to a baby. The infection may cause deformity, miscarriage, stillbirth, or death of the newborn. Some infants born with syphilis have no symptoms, but they may later present with developmental problems like seizures.

The history of syphilis

How has our understanding of syphilis evolved?

In its early stages, not much was known about syphilis and what caused it. Many countries would blame their neighboring counterparts given the stigma associated with the infection. There are many hypotheses around the origin of the infection, and many treatments were utilized throughout history until penicillin and prevention took center-stage.

How prevalent is syphilis in at-risk groups?

After chlamydia and gonorrhea, syphilis is the third most commonly reported STI in Canada. Nationally, between 2009 and 2018, the rate of infectious syphilis increased by 259%, representing the STI with the biggest increase in that period.

In 2017 in Canada, the estimated rates for men and women were: 20 cases per 100,000 men and for women, 2.4 cases per 100,000. Although syphilis can impact anyone who is sexually active, the risk is not evenly distributed, meaning that certain populations are at higher risk for syphilis. Gay, bisexual, and other men who have sex with men are known to experience high rates of syphilis. There has also been more than a 600% increase among females of reproductive age.

Some factors which may increase your risk of syphilis are: experience of violence and discrimination, mental health issues, use of crystal meth, inconsistent condom use, and multiple sexual partners. Those who experienced intimate partner violence had over two times the odds of reporting a recent syphilis diagnosis. Whereas those who experienced health care discrimination had over four times the odds of a recent syphilis diagnosis.

In 2018, 6,311 infectious syphilis cases were reported in Canada. The highest proportion of those cases were among 30-39 year-old (about 30% of the cases). The proportion of cases among women and heterosexual people is increasing. Gay, bisexual, and other men who have sex with men remain the group most affected in some provinces. There were 17 confirmed cases of syphilis passed through childbirth in 2018, which is the highest reported number in 25 years.

Syphilis myths

You will know when you have syphilis because you’ll show symptoms
Many people don’t show any symptoms, the only reliable way to know if you have an STI is to get tested.

Syphilis is very dangerous, and once you get it, it can be serious
Although syphilis can lead to complicated health outcomes, treatment can fully cure somebody from the infection. So, as long as you’re getting tested often, there’s nothing to worry about.

Syphilis is an infection from the past, it’s not very relevant nowadays
Unfortunately syphilis cases have been on the rise in Canada. It’s still a relevant STI today, which people should consider when making decisions about their sexual health.

How is syphilis transmitted?

The bacteria that causes syphilis is passed through contact with a syphilis lesion (also called sores, or chancres). Here are some ways that syphilis can be passed through:

  1. Wet kissing
  2. Anal, vaginal, or oral sexual contact
  3. Sharing sex toys
  4. Sharing injecting, snorting, or smoking drug equipment
  5. Pregnancy or birth from an infected parent

For more information around transmission, read our Syphilis Transmission article.

How to protect yourself from transmission

Preventing syphilis, alongside other STIs, can include a multitude of methods:

  1. Correct and consistent condom use for penetrative sex and of dental dams and condoms for oral sex (this does not fully eliminate risk of transmission as sores may be present in areas uncovered by condoms/dental dams)
  2. Speak to your partner about their STI and testing history
  3. Avoid having sex if you (or your partner) notice any unusual discharge, sore, or rash, around the groin area
  4. Get tested (and treated if needed) for STIs on a regular basis
  5. If you test positive for syphilis (or other STIs), treat it as soon as possible and notify your sexual partners so they can get tested as well. Ask your doctor or nurse about these!
  6. If you use drugs, avoid sharing equipment and try accessing clean/unused equipment.

Is syphilis treatable & curable?

Yes! The antibiotic benzathine penicillin G is the most commonly chosen treatment for syphilis. It’s usually delivered via-injection in the buttocks muscle. The dose of treatment chosen is based on the amount of time the infection has lived in the body. Doxycycline is sometimes used as a treatment for those who are allergic to penicillin.

Reviewed by:
Dr. Caley Shukalek

Caley is passionate about evidence-based, patient-centred care, including telemedicine that can provide high quality care from wherever a patient may choose.

He helped create Alberta's PrEP guidelines and works as a specialist in General Internal Medicine with additional training in sexual health, including HIV and sexually transmitted infections.

He holds an Masters of Public Health from Johns Hopkins University, an MD from the University of Calgary and an MSc from the University of Alberta.