What Is Syphilis?

What Is Syphilis?

Syphilis is an infection caused by the bacterium Treponema pallidum, most commonly transmitted through sexual contact. The bacterium can be transmitted through direct contact with a syphilis sore or infected mucous membranes. Sores may be present in the genital or anal area, in the rectum, in the mouth or on the lips, and may sometimes go unnoticed. Syphilis can also be transmitted from mother to baby during pregnancy. 

How is syphilis transmitted and how can it be prevented?

Transmission most commonly occurs through direct contact with an infectious sore during vaginal, anal or oral sexual contact. Condom use reduces the risk; however, contact with sores in areas not covered by a condom can lead to transmission.

1. Use condoms correctly and consistently throughout sexual contact.
2. If your partner has a sore, a rash or a syphilis diagnosis, avoid sexual contact until testing and medical assessment have been completed.
3. Talk openly with your partner about sexual health and testing.
4. Syphilis screening during pregnancy and treatment when needed are important for preventing transmission to the baby.

What are the symptoms of syphilis?

Syphilis can cause different symptoms at different stages. Even if symptoms disappear on their own, the infection may remain in the body; therefore, recovery cannot be determined solely by the disappearance of symptoms.

Early stage

The first sign may be a usually painless sore (chancre) that develops where the bacterium entered the body. The sore may appear in the genital or anal area, in the rectum or in the mouth; it may be in a location where it is difficult to notice. The sore may heal without treatment, but the infection may persist.

Secondary stage

A skin rash may also affect the palms of the hands or the soles of the feet. Fever, fatigue, sore throat, swollen lymph nodes, lesions inside the mouth or patchy hair loss may occur. Signs and symptoms vary from person to person and may be confused with other illnesses.

Latent stage

A person may have no symptoms; the infection can be detected through blood tests. The definition of this stage and the treatment approach depend on clinical information about how long the infection has been present.

Late stage and organ involvement

Untreated syphilis can affect organs and systems such as the cardiovascular or nervous system years later. Neurosyphilis, ocular syphilis and otosyphilis can develop at any stage of the infection; they are not limited to late-stage disease. Changes in vision or hearing, severe headache, or problems with balance or sensation require prompt medical assessment. 

How is syphilis diagnosed?

Syphilis is usually assessed using blood tests. Two different groups of tests are generally interpreted together for diagnosis:

1. Treponemal tests: Tests such as TPPA/TPHA or EIA/CIA detect antibodies produced against the bacterium that causes syphilis. These tests may remain positive for a long time, sometimes for life, even after successful treatment.
2. Non-treponemal tests: RPR or VDRL, together with their quantitative titres, are used to assess the infection and monitor the response to treatment. The result is interpreted alongside any previous history of syphilis and treatment information. 

If the infection is at a very early stage, blood tests may not yet be positive. If there is clinical suspicion or a history of close contact, the doctor may consider repeat testing, often within 2–4 weeks. Although testing a sample taken directly from a sore may be used in some cases, a negative PCR result alone does not rule out syphilis. If neurosyphilis is suspected, the doctor will plan cerebrospinal fluid testing based on clinical findings; this is not performed for every patient with syphilis. 

If syphilis is diagnosed or suspected, the doctor may also recommend testing for other sexually transmitted infections. Learn about the Wellcare STI test panel.

Can syphilis be treated?

Yes. Syphilis is treated with antibiotics appropriate to the stage of the disease and the patient's clinical condition. Penicillin is the preferred treatment for many stages of syphilis; a different treatment plan may be needed for neurosyphilis and eye/ear involvement. The choice and duration of treatment must be determined by a doctor. During pregnancy, penicillin is the treatment proven to protect the fetus; any history of penicillin allergy must be reported to the doctor, and specialist assessment is required during pregnancy. 

Treatment may not reverse some of the permanent damage caused by the infection. After treatment, the doctor may monitor the response using quantitative tests such as RPR or VDRL. Treponemal tests remaining positive after treatment does not, on its own, mean that treatment has failed.

Having had syphilis does not provide immunity; reinfection is possible. Assessing sexual partners and treating them when necessary helps prevent reinfection.

Syphilis during pregnancy

Syphilis screening during pregnancy is important for the health of both mother and baby. WHO recommends that pregnant women be tested at their first antenatal care visit and treated without delay if the result is positive. Untreated infection can lead to serious outcomes such as miscarriage, stillbirth, preterm birth and congenital syphilis. If testing or treatment is needed, specialists in obstetrics and gynaecology and infectious diseases should be consulted.