Syphilis is a sexually transmitted infection (STI) caused by the bacterium Treponema pallidum. This infection progresses through several stages—primary, secondary, latent, and tertiary—each with distinct symptoms and increasing severity. It is primarily spread through skin-to-skin contact during vaginal, anal, or oral sex. Left untreated, syphilis can lead to serious health problems, including neurological damage, heart issues, and even death.

Fortunately, syphilis is treatable and curable with timely diagnosis and the right antibiotics. Understanding its symptoms, causes, diagnosis methods, and treatment options can help reduce your risk of complications and promote recovery.

Stages and Symptoms of Syphilis

Syphilis is often called "The Great Pretender" because its symptoms can resemble those of other diseases. The infection progresses through four distinct stages, each marked by specific symptoms and health risks.

Primary Stage

The primary stage is the earliest phase of syphilis. Typically, a person develops one or more painless sores (chancres) at the site of infection. These may appear on the genitals, anus, rectum, lips, or inside the mouth. Chancres usually show up 10 to 90 days after exposure and heal on their own within three to six weeks, even without treatment. However, the infection remains in the body and progresses if left untreated.

Secondary Stage

In the secondary stage, the infection spreads throughout the body. This stage is characterized by a skin rash, which often appears on the palms of the hands or soles of the feet. The rash may not cause itching and can vary in appearance. Other symptoms include fever, sore throat, swollen lymph nodes, fatigue, muscle aches, and mouth or genital ulcers. Like the primary stage, symptoms may resolve on their own, but the bacteria remain active in the body.

Latent Stage

The latent stage is a period where the infection is inactive. No visible symptoms are present, but the bacteria continue to live in the body. This stage can last for years. In some cases, the infection may remain dormant permanently, while in others, it progresses to the most severe stage—tertiary syphilis.

Tertiary Stage

Tertiary syphilis is the most dangerous phase. It may develop 10–30 years after the initial infection if syphilis is left untreated. This stage can cause serious damage to internal organs, including the heart, brain, nerves, liver, bones, and eyes. Complications may include neurosyphilis (affecting the nervous system), ocular syphilis (impacting the eyes), and otosyphilis (affecting hearing). Without treatment, tertiary syphilis can be fatal.

Causes and Transmission of Syphilis

Syphilis is caused by Treponema pallidum, a spiral-shaped bacterium. It spreads mainly through direct contact with syphilitic sores, often during vaginal, anal, or oral sex. These sores can be found on external genitals, in the vagina or rectum, or in or around the mouth.

It is also possible for a pregnant individual to transmit syphilis to their baby during pregnancy or childbirth. This is called congenital syphilis and can cause severe complications or even death in newborns.

Syphilis is not spread through casual contact. You cannot get it from sharing toilet seats, eating utensils, doorknobs, bathtubs, or swimming pools.

Risk Factors for Syphilis

Anyone who is sexually active can get syphilis, but some groups are at higher risk. These include:

  • People with multiple sexual partners

  • Men who have sex with men (MSM)

  • People living with HIV

  • Individuals who engage in unprotected sex

  • Pregnant people who have not been screened for STIs

Regular testing and open communication with healthcare providers can help prevent the spread of syphilis.

Diagnosis of Syphilis

To diagnose syphilis, healthcare providers typically use two types of blood tests:

  • Nontreponemal tests: These include the Rapid Plasma Reagin (RPR) and Venereal Disease Research Laboratory (VDRL) tests. They detect antibodies that the body produces in response to syphilis infection, but not specifically to the syphilis bacteria.

  • Treponemal tests: These confirm the infection by detecting antibodies specific to Treponema pallidum. Tests include Fluorescent Treponemal Antibody Absorption (FTA-ABS) and Treponema pallidum particle agglutination assay (TP-PA).

In some cases, a swab from a syphilitic sore may be tested using Polymerase Chain Reaction (PCR) to directly detect the bacteria. This is usually done only when active lesions are present.

Treatment Options for Syphilis

Syphilis is easily curable in its early stages. Penicillin G benzathine is the preferred treatment for all stages of syphilis. The route and duration of treatment depend on the stage of infection.

  • Primary, Secondary, or Early Latent Syphilis: A single intramuscular injection of benzathine penicillin is typically sufficient.

  • Late Latent or Tertiary Syphilis: A longer treatment course is required—three weekly injections of penicillin.

  • Neurosyphilis or Ocular Syphilis: Requires intravenous penicillin administered every four hours for 10–14 days.

Alternatives for People Allergic to Penicillin

For individuals who cannot tolerate penicillin, alternative antibiotics include:

  • Doxycycline

  • Ceftriaxone

  • Tetracycline

However, these alternatives may be less effective, especially for advanced stages or neurosyphilis. Pregnant people allergic to penicillin usually undergo a penicillin desensitization procedure before receiving treatment.

Monitoring and Follow-Up

After treatment, your provider will schedule regular follow-up blood tests—usually at 3, 6, and 12 months. These tests help ensure the infection has been cured and to detect any signs of reinfection.

A temporary reaction called the Jarisch-Herxheimer reaction may occur within 24 hours of starting treatment. This is not an allergic reaction but a short-term flu-like response as the bacteria die off.

Complications of Untreated Syphilis

Without treatment, syphilis can lead to severe health problems, particularly in the tertiary stage. These include:

  • Permanent damage to the heart and blood vessels

  • Neurological disorders, such as memory loss, coordination issues, and dementia

  • Vision loss due to ocular syphilis

  • Hearing loss from otosyphilis

  • Paralysis or stroke

  • Mental illness

  • Death

Pregnant individuals with syphilis are at high risk of miscarriage, stillbirth, or delivering a baby with congenital syphilis.

How to Prevent Syphilis

While complete abstinence from sex is the only guaranteed way to prevent syphilis, most people rely on other protective measures. These include:

  • Using condoms or dental dams during vaginal, anal, or oral sex

  • Limiting the number of sexual partners

  • Getting tested regularly, especially if you’re in a high-risk group

  • Encouraging your partner(s) to get tested and treated

  • Avoiding sexual contact with anyone who has visible sores or rashes

Pregnant people should be tested for syphilis early in pregnancy and again during the third trimester if at high risk.

Living With Syphilis

With proper diagnosis and treatment, syphilis can be completely cured. However, it’s important to take all medication as prescribed and follow through with regular testing. Some damage caused by untreated syphilis may be irreversible, so early detection is critical.

It’s also important to refrain from any sexual activity until sores are healed and treatment is completed. Even after successful treatment, you can be infected again if you are exposed to syphilis from an untreated partner.

Having open, honest communication with your healthcare provider and sexual partners helps reduce the risk of reinfection and promotes a healthier sexual life.

A Quick Review

Syphilis is a common but serious STI caused by the bacterium Treponema pallidum. It progresses through four stages, each with increasingly severe symptoms. Syphilis is transmitted through direct contact with infected sores during sexual activity or from parent to child during pregnancy.

Diagnosis is made through blood tests, and treatment is highly effective, particularly when started early. Penicillin remains the most effective treatment option, with alternatives available for those who are allergic.

Untreated syphilis can lead to severe health consequences, including damage to the brain, heart, and other organs. Regular STI testing, using protection, and treating partners are essential strategies for prevention.

Early diagnosis and treatment can ensure full recovery and prevent long-term complications. Stay informed, practice safe sex, and consult a healthcare provider if you have any concerns or symptoms.