What Is Syphilis?

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Syphilis is one of the better-known sexually transmitted infections (STIs), also referred to as a sexually transmitted disease (STDs). It is caused by the bacterium Treponema pallidum and can often be recognized by the appearance of an open ulcerative sore, known as a chancre, on the genitals, mouth, anus, or rectum. Antibiotics can treat syphilis, but the course depends on which stage the infection is in (primary, secondary, latent, and tertiary). Each stage has its characteristic signs and symptoms—and potential complications.

While the rate of syphilis infections dropped dramatically with the use of intramuscular penicillin in the 1940s, many of those gains have been reversed in recent years.

Today, the disease affects more than 27,000 Americans annually and over 6 million individuals worldwide.

Though the very thought of syphilis can be distressing, the infection is often easily treated if recognized and detected, and readily avoided with the use of condoms and a reduction in the number of sex partners.

Stages of Syphilis
Verywell / Emily Roberts

Symptoms of Syphilis

The symptoms of syphilis are characterized by the stage of infection. While some symptoms are unmistakable, others are less distinctive and may be misdiagnosed.

  • Primary syphilis will often manifest with a chancre, usually within 21 days of exposure. Because chancres are usually painless and internal, they can be easily missed by both patients and doctors. Without treatment, a chancre will heal in anywhere from three to six weeks.
  • Secondary syphilis occurs within four to 10 weeks of a primary infection. One of the characteristic symptoms is a widespread rash on the trunk, limbs, and (most tellingly) the palms and soles of the feet. Flu-like symptoms may accompany the rash. There are, however, cases that can manifest themselves in more unusual ways. Symptoms tend to resolve without treatment in three to six weeks.
  • Latent syphilis is marked by the relative absence of symptoms, lasting anywhere from years to decades, and is based on blood tests. For diagnostic purposes, the stage is further described as being either early latent (less than a year from the last blood test) or late latent (more than a year from the last blood test).
  • Tertiary syphilis is the most serious stage of infection. It's characterized by major diseases of the skin, bones, heart, liver, and other organs. Neurosyphilis, arguably the most severe complication, affects the brain and is one of the most difficult to treat.

Congenital syphilis is a serious medical condition in which an infected mother passes syphilis to her unborn baby. In addition to lung, liver, spleen, and brain disorders, congenital syphilis can lead to physical and facial malformations, developmental delays, and intellectual disability.


Treponema pallidum is a spiral-shaped bacterium that only causes disease in humans. Its corkscrew shape allows it to burrow into mucous membranes or enter minute breaks in the skin.

Syphilis is transmitted almost exclusively through oral, vaginal, or anal sex, or from mother to child during pregnancy.

Less commonly, syphilis can be passed through kissing if broken skin comes into contact with an open sore. Syphilis cannot be passed through toilet seats, casual contact, or shared utensils or personal care items.

There are certain factors that can increase a person's risk of infection:


Syphilis testing is a two-step process in which non-treponemal tests (which can detect damage caused by T. pallidum ) are used alongside treponemal tests (which can detect the bacterium itself). Both are blood-based tests. Because the non-treponemal tests are more sensitive, they are generally performed first. If the tests are positive, the treponemal test would be used to confirm the diagnosis.

With blood testing, syphilis can usually be detected within a week or two of exposure. The most accurate results can be obtained during the first three months, while the rate of false positives steadily increasing after 90 days.

Blood, tissue, and body fluids can also be directly tested using a procedure known as dark-field microscopy. While less commonly used today (due to the need for highly skilled technicians), dark-field microscopy can provide doctors with definitive, visual evidence of an infection. It can be used during very early infection or in later-stage disease when infections are harder to diagnose.


Syphilis infections can be cured with antibiotics. Penicillin (via injection) is considered the drug of choice, but others (such as doxycycline, tetracycline, azithromycin, or ceftriaxone) may be used if a person is allergic to penicillin.

The treatment of syphilis can vary by the stage of infection:

  • Primary, secondary, and early latent syphilis can be treated with a single injection of penicillin.
  • Late latent syphilis would require three shots, each given in one-week intervals.
  • Tertiary syphilis would be treated in the same manner as late latent syphilis if the brain and central nervous system are not involved.
  • Neurosyphilis requires an extensive 10- to 14-day course of treatment, either with intramuscular penicillin or a combination of penicillin shots and oral medications.

Even if a tertiary infection is cleared, any harm done to the brain or other organs may be irreversible. Additional interventions, including surgery, may be needed to help manage or repair the damage.


Condoms remain the first-line defense against sexually transmitted diseases like syphilis. While condoms are not infallible (especially if you don't use them correctly), they are the most reliable form of prevention short of abstinence.

Equally important is a reduction in the number of people you have sex with, particularly those who are anonymous.

In the end, the more people you have sex with, the greater your odds of infection.

To protect yourself and others, you may want to consider getting an STD test from your doctor or local clinic. The U.S. Preventive Services Task Force currently recommends that people at increased risk of infection be screened. This includes MSM, injecting drug users, or people who have multiple sex partners and/or engage in unprotected sex.

A Word From Verywell

While certain people are at greater risk of syphilis than others, don't fool yourself into thinking that you are safe simply because you don't "sleep around." According to statistics from the Centers for Disease Control and Prevention, syphilis rates in the United States have risen every year since 2001 an between 2017 and 2018 they increased by 13.3 percent.

If in doubt about your status, do yourself a favor and get tested. Even if you test positive, the earlier you know, the faster you can be treated—and the less likely you will be to infect others.

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