Syphilis is a bacterial infection (Treponema pallidum) that is most often spread by sexual contact. The infection usually causes disease over a course of several years. In the early stages, syphilis causes disease of the genitals, mucous membranes and skin. If it is not treated, syphilis can lead to serious problems, such as heart problems, neurological problems (neurosyphilis), blindness, dementia, and death.

Since 1996, rates of syphilis have been increasing in the United States, notably among men who have sex with other men.

Syphilis is passed from person to person through direct contact with a syphilis sore or lesion, usually during vaginal, anal or oral sex. Pregnant women with the disease can pass it to the babies. Syphilis cannot be spread by toilet seats, door knobs, swimming pools, hot tubs, bath tubs, shared clothing, or eating utensils.

While the health problems caused by syphilis in adults and newborns are serious in their own right, the genital sores caused by syphilis in adults also make it easier to sexually transmit or acquire HIV infection.

Studies suggest that people with HIV who become infected with syphilis may be more likely to develop lesions and may have a faster progression of syphilis disease. A person with HIV may also temporarily see their CD4 cells drop and HIV levels rise during early syphilis, but then improve after being treated.

What are the symptoms?

Syphilis is actually a single disease made up of several different stages. The symptoms of syphilis depend on the stage of disease.


Primary syphilis: In most cases, the only noticeable symptom of primary syphilis is a painless sore (called a “chancre”) that develops within two to six weeks after someone has been infected with T. pallidum. The sore usually develops on the penis, vulva, vagina or anus. It can also develop on the cervix, tongue, lips, and other parts of the body. The sore usually heals within a few weeks without treatment.

HIV is much easier to transmit when these sores are present. Someone who is HIV positive and has a syphilis sore is much more “infectious”—that is, likely to transmit his or her HIV—than someone who does not have a chancre. Similarly, HIV-negative people who have a syphilis sore are at a much higher risk of becoming infected with HIV if they have unprotected sex with someone who is HIV positive.

If you have primary syphilis and do not receive treatment, it’s possible that your infection will progress to secondary syphilis.


Secondary syphilis: The most common symptom of secondary syphilis is an outbreak of small, pox-like lesions—usually brownish-pink in color—that seem like a non-itchy rash when clustered together. They can appear anywhere on the body, but a rash and lesions on the palms and soles of the feet are classic symptoms of secondary syphilis.

These lesions are highly contagious. They can spread the bacteria if the skin is broken. They can also take several weeks or months to heal, and possibly recur, without treatment.

Secondary syphilis can occur months to years after primary syphilis, and can last two years or more. Other possible symptoms of secondary syphilis include fever, fatigue, soreness and aching.

Latent syphilis: Latent (hidden) syphilis is diagnosed when a person has antibodies to the bacterium but doesn’t have any symptoms of the infection. Even though someone with latent syphilis generally isn’t considered infectious—meaning that they are unlikely to transmit the bacteria to others—treatment is recommended to prevent serious late-stage disease complications.

Latent syphilis can either be early latent or late latent, depending on how long someone has had the infection. People with late latent syphilis (those who have been infected for at least a year) or latent syphilis of unknown duration (those who don’t know how long they’ve been infected) require more aggressive treatment than those who with early latent infection (those who have been infected for less than a year).


Tertiary syphilis: If primary, secondary or latent syphilis is not treated, the bacteria can spread and damage internal organs, including the brain, nerves, eyes, heart, blood vessels, liver, bones and joints. This can lead to a variety of serious health problems, including stroke, paralysis, aneurysms, and heart disease.


Neurosyphilis: This occurs when T. pallidum infects the brain or spinal cord (central nervous system). Infection can occur during any syphilis stage and can cause serious neurological damage, including paralysis, numbness, gradual blindness and deafness. Neurosyphilis can be serious enough to cause permanent disability or death. Studies have found that HIV-positive people infected with T. pallidum are more likely to develop neurosyphilis, even during the early stages of infection.

How is syphilis diagnosed?

Syphilis is known as the “great imitator.” This is because many of the symptoms of syphilis are the same as those seen in other diseases. In turn, laboratory tests are necessary to diagnose syphilis.

There are two ways to diagnose syphilis. If you have a sore (primary syphilis) or pox-like lesions (secondary syphilis), your doctor can collect a small sample and send it to a lab for examination under a microscope. Your doctor can also collect a sample of blood and send it to a lab for analysis. During the first two to three weeks of infection, there is a possibility of a blood test coming back negative when in fact you are positive (a false-negative result). Another test, using the same sample of blood, can be done to confirm whether or not the bacterium is present. 

How is syphilis treated?

Injections of penicillin are the most effective treatment for syphilis. In fact, penicillin is a cure for syphilis. The amount of penicillin used to treat syphilis depends on the stage of infection. There are not sufficient studies to recommend alternatives to penicillin for people who are allergic to the drug. For such individuals, it is recommended that they undergo penicillin desensitization.


Primary and secondary syphilis: For HIV-positive and HIV-negative people, one injection of penicillin is all that’s usually needed. However, some experts recommend one injection every week for three weeks (a total of three injections) for HIV-positive people. This often depends on the overall health of the immune system—the lower the CD4 cell count, the less likely it is that syphilis will be cured with just one injection. In either case, follow-up blood tests should be done to make sure the treatment successfully cured the syphilis.


Latent syphilis: HIV-negative and HIV-positive people with early latent syphilis are generally treated with one injection of penicillin (HIV-positive people with early latent syphilis should be tested for neurosyphilis first, to determine if intensified treatment is necessary). HIV-negative and HIV-positive people with late latent syphilis—or those who don’t know how long they’ve been infected with syphilis—should receive one penicillin injection every week for three weeks (a total of three injections).

Tertiary syphilis: HIV-negative and HIV-positive people with tertiary syphilis should receive one penicillin injection every week for three weeks (a total of three injections). They should also be examined for signs and symptoms of neurosyphilis to determine if more aggressive antibiotic treatment is necessary.


Neurosyphilis: Treating neurosyphilis often requires hospitalization. The treatment consists of penicillin administered through an intravenous (IV) line every four hours for up to two weeks. Treatment guidelines from the Centers for Disease Control and Prevention (CDC) in Atlanta recommend that everyone diagnosed with syphilis should also be carefully evaluated for neurosyphilis with both a physical examination and tests of spinal fluid. People suspected of having neurosyphilis should be treated for it even if treponemal spinal fluid tests fail to confirm the diagnosis.

Penicillin injections are administered directly into the butt muscle. Your butt may feel sore for several days after each injection. If you have a known allergy to penicillin, make sure you tell your doctor before you receive an injection. There are other antibiotics that can be given if you are allergic to penicillin. Due to a higher rate of first-line treatment failures among pregnant women, some doctors recommend that pregnant women diagnosed with syphilis receive a second injection one week after the first.

Some people become ill after receiving their first penicillin injection. This is because of a “Herxheimer reaction,” named after a German doctor who first noted it in 1895. Because penicillin injections are so fast-acting against the bacterium that causes syphilis, it can cause the bacteria to release high levels of toxins as they die. This can cause symptoms, such as high fever, profuse sweating, night sweats, nausea, and vomiting. The symptoms of Herxheimer reactions usually end within a few hours, and can often be managed with the use of aspirin, NSAIDs (non-steroidal anti-inflammatory drugs), Benadryl, pain medication, muscle relaxers, or others remedies. You should talk with your doctor or a nurse about your options.

Can syphilis be prevented?

Yes. Two people who know that they are not infected and who have sex only with each other cannot contract syphilis. If you have sexual relations with someone and do not know if he or she has syphilis, a good defense against becoming infected is to use a latex condom during anal or vaginal intercourse. However, condoms do not provide complete protection because syphilis sores or lesions can sometimes be on areas not covered by a condom.

Syphilis can be cured—and will not lead to serious damage to the organs—if it is caught and treated during its earliest stages. If you notice any unusual sores in or around your genitals, or think you may have had sexual relations with someone who has syphilis, you should discuss the possibility of testing with your health care provider. In fact, if you are sexually active with multiple partners, you should consider getting tested regularly—it’s a simple blood test.

Finally, it’s important to know that even if you treat & cure a syphilis infection, you can still become reinfected in the future.

Are there any experimental treatments?

If you would like to find out if you are eligible for any clinical trials involving new treatments for syphilis, visit, a site run by the U.S. National Institutes of Health. The site has information about all HIV-related clinical studies in the United States. For more info, you can call their toll-free number at 1-800-HIV-0440 (1-800-448-0440) or email

Last Reviewed: February 10, 2016