Syphilis

Medically Reviewed on 1/29/2024

What is syphilis?

Illustration of a syphilis bacterium.
Illustration of a syphilis bacterium.

Syphilis is a sexually transmitted infection (STI) caused by the bacteria Treponema pallidum. Spread of the infection occurs during intercourse when there is contact with the open sore of syphilis, called a chancre. Vaginal, oral, and anal intercourse are all methods of transmission.

Syphilis may also spread from a pregnant mother to the fetus through the placenta.

If left untreated, syphilis can progress through three stages and cause damage to multiple organs of the body.

What causes syphilis? How do you get syphilis?

Syphilis is an extremely common infection. World Health Organization estimates show more than 6 million new cases each year.

Syphilis is a reportable disease in the US. In 2021, the Centers for Disease Control and Prevention (CDC) reported more than 176,000 new cases of syphilis and more than 2,800 new cases of congenital syphilis.

Sexual transmission

Syphilis can spread through vaginal, oral, or anal intercourse.

The risk of infection with syphilis depends on a person’s sexual activity. Risk is minimized for those in a mutually monogamous relationship with a person who has tested negative for the infection and who uses condoms correctly with every sexual contact.

Can you get syphilis non-sexually?

Congenital transmission

Treponema pallidum, the bacteria that causes syphilis, can pass from the pregnant mother through the placenta to the unborn fetus. There is routine screening for syphilis in the first trimester of pregnancy.

Blood and organ transmission

While it is possible for syphilis to spread through blood transfusions, it is extremely rare. As a result of strong blood screening and storage guidelines, no case of transfusion related syphilis has been reported in the United States for more than 40 years.

Similarly, in organ transplants, donor organs are tested for all manner of infection prior to transplant.

What are the stages and symptoms of syphilis?

If left untreated, syphilis will progress through different clinical stages of the disease, often described as early and late.

Primary and secondary syphilis are early stages.

Latent (asymptomatic) and tertiary syphilis are late stages.

QUESTION

Condoms are the best protection from sexually transmitted diseases (STDs). See Answer

Early stages and symptoms of syphilis: primary and secondary

Primary syphilis

Primary syphilis begins with the formation of a painless ulcer called a chancre. While this is most often a single sore, multiple chancres may develop. The chancre is usually 1-2 cm (1/2-3/4 inches) in diameter with a raised or heaped up margin. It contains infectious bacteria and while the open sore is present, the condition is highly contagious. Swollen lymph nodes may also be observed.

Lesions typically heal in 3 to 6 weeks, but the infection begins spreading throughout the body. Because the lesion is painless, and heals on its own, some people may not seek treatment.

The open sore is teeming with bacteria and is very infectious. While the chancre may be seen on the penis, lesions in other parts of the body, like the vagina, anus or throat, may not be so obvious.

Secondary syphilis

If left untreated, symptoms of secondary syphilis may occur in about 25% of patients. It may take weeks to months for this to occur, and the patient may not even remember the initial sore.

Secondary syphilis is characterized by a non-itchy skin rash that is similar to many other rashes associated with infection. It tends to be a combination of flat and raised areas (maculopapular), symmetric, and involves the whole body, trunk, extremities. As opposed to many other rashes, syphilis will be present on the palms of the hands and soles of the feet. In some people, the rash may be mild and not noticed. Up to 20% of patients with secondary syphilis will not have a rash.

Raised gray or whitish patches of skin, known as condyloma lata, may also develop, particularly in warm and moist areas of the body such as the armpits, mouth, or groin. There can be multiple swollen lymph nodes in the neck, armpits, and groin.

Secondary syphilis is an infection that spreads throughout the body, and produces other symptoms including:

If left untreated, the infection may progress to tertiary syphilis.

Late stages and symptoms of syphilis: tertiary and latent

Tertiary syphilis

After the symptoms of secondary syphilis resolve, if left untreated, the infection remains latent in the body. Up to 40% of these patients will eventually develop tertiary syphilis. It can develop within a year or up to 20 years after the initial infection. Tertiary syphilis is associated with damage to any number of organ systems, but most commonly the heart and brain.

Aortic syphilis describes an infection of the ascending aorta, where the large blood vessel leaves the heart. The walls of the aorta become inflamed and the aorta can dilate and calcify forming an aneurysm. It can also cause the aortic valve that connects the heart to the aorta to fail (aortic valve regurgitation).

Neurosyphilis is the term used to refer to the involvement of the central nervous system and alterations in neurologic function.

Latent syphilis

Patients who are infected with syphilis, but have no visible symptoms of the disease, may develop latent syphilis.

Early latent syphilis describes those who are within a year of being infected. They are still potentially infectious to others because of lesions that they are not aware of, perhaps in parts of the body that are not visible, like the anus, vagina, or throat.

After a year from infection, latent syphilis patients are not infectious to their partners.

The diagnosis of latent syphilis is made by blood test, since by definition there are no visible symptoms.

Neonatal or congenital syphilis stages and symptoms

In pregnant women with untreated syphilis, the risk of stillbirth or death in the neonate’s first month of life can be greater than 30%.

Symptoms may occur in the newborn at onset, or can be delayed up to two years.

Early neonatal syphilis can present as a stillbirth, or with symptoms that involve almost any organ system.

Late presentation syphilis in infants older than two years of age can include skin and bone abnormalities, eye and ear issues, seizures, and more.

All pregnant women should get tested for syphilis in the first trimester. Testing should be repeated in the third trimester for those at high risk of infection.

Diagnosis of syphilis

While the presence of a chancre sore can strongly suggest the diagnosis of syphilis, blood tests are used to confirm the diagnosis.

Blood tests make the presumptive diagnosis from antibodies to the Treponema pallidum bacteria. Tests are not available to directly establish the presence of the bacteria. For this reason, blood tests need to be interpreted as to whether there is a new infection present, whether the antibodies are left over from a previous infection, or whether the result is a false positive and the disease is not present.

About 1 to 2% of the US population will have false positive tests. Some reasons for this include recent immunizations and autoimmune diseases.

What is the treatment for syphilis?

Penicillin is the antibiotic treatment of choice for all stages of syphilis.

In early syphilis:

  • penicillin is given as a single intramuscular injection
  • for patients with penicillin allergies, the alternative is doxycycline (tetracycline) taken by mouth for 2 weeks

In late syphilis:

  • penicillin is given weekly for 3 weeks
  • for patients with penicillin allergies, doxycycline will be taken by mouth for 4 weeks

In neurosyphilis:

  • penicillin is given intravenously every 4 hours for 10 to 14 days
  • for patients with penicillin allergies, ceftriaxone is used intravenously for 10 to 14 days

When non-penicillin antibiotics are used, monitoring of patient response is recommended to ensure the infection has been completely treated. This is done by measuring antibody levels in the blood.

In pregnancy

  • penicillin is safe and is given intramuscularly
  • for patients with penicillin allergies, doxycycline cannot be used because it can damage the bones and teeth of the fetus, the recommendations is to attempt to desensitize the patient so that penicillin can be used
  • if penicillin is not possible, erythromycin, azithromycin, or ceftriaxone are recommended. These alternatives may not work as well, or may not cross the placenta to help treat the fetus

How long does it take to treat and cure syphilis?

Depending upon the stage of syphilis and the antibiotic used, the treatment may involve just one injection. More complicated or later stage syphilis may take 2 to 4 weeks to complete the course of antibiotics.

In up to a third of patients, the Jarisch-Herxheimer reaction may occur in the first 24 hours after the antibiotic treatment. The patient may experience fever, sweats and chills, muscle aches, and worsening rash. Severe reactions are rare and can also include difficulty breathing and seizures.

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What are the complications of syphilis?

What happens if syphilis is left untreated?

Untreated syphilis spreads throughout the body and damage or failure of almost any organ in the body. Tertiary syphilis complications may affect the brain and cause blindness, deafness, stroke, and dementia. The heart and aorta can also be affected. Other organs including the liver and kidney are at risk. Late-stage syphilis can be fatal.

Untreated syphilis in pregnant women may lead to fetal or neonatal death in greater than 30% of patients.

What is the prognosis for syphilis?

The goal of treatment is to cure of the patient. Primary and secondary syphilis is curable with antibiotic treatment. However, if the diagnosis is not made or delayed and treatment is not provided, there is the risk of progression to late stage/tertiary syphilis with the possibility of long-term symptoms, organ failure, and death.

Is syphilis completely curable?

Syphilis is curable. The treatment for syphilis is antibiotics, preferably penicillin. The length of time needed for treatment depends upon the stage of syphilis.

It is important to monitor the effects of the treatment to ensure the disease is completely treated and eradicated.

Can syphilis be prevented?

There is no vaccine available to prevent syphilis.

The use of safe sex practices, including condom use for every sexual encounter, decreases the risk of infection. Washing or douching after sexual activity does not prevent infection.

It is not always possible to know whether a sexual partner is infected with syphilis because the chancre (ulcer) may be located in the vagina, anus, or mouth.

Neonatal syphilis is prevented by screening all pregnant women and treating those who are infected.

Medically Reviewed on 1/29/2024
References
Centers for Disease Control and Prevention. Sexually Transmitted Disease Surveillance. Updated. 11Apr2023.
https://www.cdc.gov/std/statistics/2021/default.htm

Association for the Advancement of Blood and Biotherapies. Syphilis. Updated: 15Nov2023.
https://www.aabb.org/regulatory-and-advocacy/regulatory-affairs/infectious-diseases/syphilis

Workowski KA, Bachmann LH, etal. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021. 23;70(4):1-187

Ghanem KG, Workowski KA. Management of adult syphilis. Clin Infect Dis. 2011. 53 Suppl 3:S110-28.

Cooper JM, Sánchez PJ. Congenital syphilis. Semin Perinatol. 2018. 42(3):176-184.