Syphilis is a sexually transmitted disease (STD), which, like many other STDs, is caused by bacteria.1 The bacterium specific to syphilis is known as Treponema pallidum. It can spread to a person if he or she comes in contact with a syphilitic sore, also known as a chancre, during sexual activity.1

Syphilis can affect the genitals (penis, vagina, and cervix), rectum, lips, mouth, and anus of both men and women. In addition to sexual transmission, syphilis can also be spread to infants during vaginal birth in women who have the STD while pregnant.

While any sexually person can develop syphilis, it's generally most common in men, and particularly in men who have sex with other men.

Prevalence of Syphilis

Syphilis is more common than many people realize, and it affects certain people at different rates. For example, in 2017 over 101,000 new diagnoses of syphilis—the majority of them occurring in men who have sex with men—were reported to the Centers for Disease Control and Prevention (CDC).1,2 That's more than the total number of new cases of human immunodeficiency virus (HIV) reported in the year before.

Additionally, 918 cases of congenital syphilis (mother-to-infant transmission) occurred in 2017, well over the 99 estimated cases of 99 perinatal HIV infection in the year prior. Of these 918 cases, they occurred at a 6.1 times higher and 3.5 times higher rate in infants born to black and Hispanic mothers (respectively) compared to white mothers.1

Signs and Symptoms of Syphilis

Known as the "Great Pretender" because it can mimic so many other types of diseases and illnesses, syphilis has different signs and symptoms depending on its disease stage—which can span a matter of week, months, or even years.1

Symptoms of syphilis will typically show up about three weeks after initial infection, but it may take up to 3 months in some cases. The following symptoms are the most commonly reported, in order of disease progression:

  • Syphilitic sores, called chancres, which are typically painless, firm, and round. They will last up to 3 to 6 weeks.
  • Rashes on the skin near the mouth, vagina, penis, anus, or elsewhere on the body, including the palms and bottom of the feet. These rashes (which occur after the initial chancres heal) are often not itchy but can look like rough, red, or brown spots. Alternatively, a syphilis rash may be barely noticeable.
  • Large white or gray skin lesions called condyloma lata, which tend to develop in moist areas like the mouth, groin, or axilla (armpits).
  • Unusual patchy hair loss
  • Flu-like symptoms, including swollen lymph glands, sore throat, headaches, weight loss, fever, muscle aches, and fatigue.

The above symptoms will eventually go away, whether a person is treated for syphilis or not. However, even without symptoms syphilis can continue to progress if the affected person does not seek appropriate diagnosis and treatment.

This resolution of symptoms helps to explain the so-called "latent stage" of syphilis. During this stage, people with syphilis will have no notable signs or symptoms despite being infected with the STD (and despite being able to transmit the STD to sexual partners).

Consequences and Complications of Syphilis

While rare, serious and sometimes life-threatening consequences of syphilis can develop.1 These more severe complications almost always occur in untreated and advanced cases.

Complications may include:

  • Tertiary syphilis: occurring about 10 to 30 years after initial infection, tertiary syphilis is a potentially fatal condition involving multi-system organ damage. A person's eyes, nerves, liver, bones, brain, heart, and joints can be impacted, and symptoms will depend on the tissues affected.
  • Neurosyphilis: when the syphilis bacteria affects the nervous system, specific symptoms can develop, including headache, behavior and personality changes, sensory and coordination deficits, memory loss, and dementia. This can occur at both early and late stages of the disease.
  • Ocular syphilis: this complication—hallmarked by syphilis infection in the eye—can lead to vision loss and eventual blindness, and can also occur at early and late stages of the disease.
  • Stillbirth: for pregnant women who have untreated syphilis, their risk of experiencing infant death can be as high as 40%.1 Because syphilis can threaten an unborn child's life, the CDC recommends that all pregnant women should be screened for this STD at her first prenatal appointment.
  • Meanwhile, babies born alive who are infected by syphilis may not shown any initial symptoms but can experience life-threatening complications within a matter of weeks, including seizures and developmental delays.

Another complication of syphilis is that having it can significantly increase a person's risk for contracting HIV. The CDC estimates that a person with syphilis is up to 5 times more likely to acquire HIV if exposed to the virus compared to someone without syphilis.1

Treatment for Syphilis

Syphilis is curable with the right treatment, and the earlier treatment can begin, the better the outcomes will be.

Following a diagnosis (which generally involves two blood tests), the person with syphilis will be prescribed penicillin or another type of antibiotic. Depending on the time of diagnosis and stage of the disease, a person may require additional treatments to manage or resolve secondary damage caused by the STD.

While appropriate treatment can cure a person of their syphilis, having the STD once does not prevent a person from contracting it again from a future infected partner. Because chancres can occur in places that are not covered by condoms, it's important to realize that condoms can reduce but not completely eliminate the risk of contracting syphilis, especially for higher-risk individuals (including men who have sex with men, people taking PrEP for HIV prevention, and sexually active people living with HIV).

Are you overdue for a STD screening? If you're sexually active, it's in the best interest of yourself and your partner(s) to be screened regularly. Depending on your unique risk factors and lifestyle, syphilis may be important to include in your screening.