Treponema pallidum


The causative agent of syphilis (lues), Treponema(T.) pallidum, is a bacterium that belongs to the spirochete family. Transmission occurs mainly through sexual intercourse. The disease progresses in several stages if untreated and may last for months to years. Spontaneous recovery is possible.



Pathogen reservoir

Transmission occurs exclusively from person to person

Infection route

Infection usually occurs through sexual contact. Transmission from mother to child is also possible during pregnancy and at birth. Transmission via blood transfusions has been described in isolated cases. Treponemas are highly infectious. In the case of sexual contact with an infected person in stage I or II, the risk of transmission is around 30%.

Incubation period

Two to three weeks, up to 90 days are possible.


The course of a syphilis infection can be divided into four different stages. For details on the individual stages, see the technical information.


The first-line treatment for syphilis is intramuscular administration of penicillin G. The duration of treatment varies depending on the stage. In case of penicillin allergy, other antibiotics can be used.


The most important preventive measure to avoid transmission is the correct use of condoms during sexual contact. Contact with ulcers and open skin sites should generally be avoided, as these are highly infectious.

Situation in Austria

Since syphilis is not a notifiable disease in Austria, there are no official case figures in this country. An overview of the case numbers in Europe can be found in the annual epidemiological report of the ECDC

Specialized information


The first phase, primary syphilis, is characterized by the appearance of a mostly painless ulcer with a hardened border. This "ulcus durum" or "hard chancre" usually occurs at the site of infection, i.e. on the penis, vulva or also in the anal region. It is usually accompanied by painless lymphadenitis. The ulcer usually heals with scarring within six weeks.

In the second stage, secondary syphilis, there are general symptoms with swelling of the lymph nodes and flu symptoms as well as a very broad and variable spectrum of skin and mucous membrane symptoms that resolve spontaneously after three to six weeks, even if untreated.

This is followed by a dormant stage (lues latens) in which no symptoms occur despite positive detection of the pathogen.

In about one third of all inadequately treated patients, gummatous, tumor-like tissue changes form in the third stage, tertiary syphilis, which can occur in all organs and secrete an inflammatory secretion when they appear on the skin. In the cardiovascular system, inflammation may occur in the great vessels, especially in the aorta, and also aortic aneurysms. If the central nervous system is affected, the disease is referred to as neurosyphilis. This can already occur in the primary and secondary stages of the disease or as a late manifestation in the fourth stage of syphilis infection (quaternary syphilis).

Quaternary syphilis may be asymptomatic, meaning that no symptoms occur despite evidence of involvement of the nervous system. If the stage is symptomatic, possible manifestations include strokes, sensory and balance disturbances, signs of meningitis, seizures, progressive paralysis, dementia, and personality changes.

A combination of clinical and laboratory diagnostic tests should always be performed to diagnose syphilis.


The first-line treatment for syphilis is intramuscular administration of penicillin G. The duration of treatment varies depending on the stage of the disease. The duration of treatment varies depending on the stage: while a single dose is sufficient for early syphilis, three injections spread over 15 days are administered for late syphilis. If neurosyphilis is present, penicillin G should be administered intravenously; the recommended duration of treatment is 14 days.

In case of penicillin allergy, doxycycline or ceftriaxone may be used alternatively.

A frequent complication of therapy is the Jarisch-Herxheimer reaction: here, due to the decay of the pathogen under antibiotic therapy, bacterial endotoxins are released, leading to an uncontrolled immune response and an acute systemic inflammatory reaction. This is manifested by the onset of fever and flu symptoms within a few hours after initiation of therapy. Tachycardia, rise or fall in blood pressure, seizures and other symptoms may occur. Glucocorticoids can be used for drug therapy, although these should be administered prophylactically from the secondary stage onwards.


Dark-field microscopy is suitable for direct pathogen detection from genital primary effects or from weeping efflorescences of the secondary stage. Molecular biological methods such as PCR can be used especially in cases of clinical suspicion of an early primary effect. However, a negative result of these diagnostic methods does not exclude syphilis with certainty.

In practice, purely serological tests are usually used for antibody detection. ELISA (enzyme-linked immunosorbent assay), TPHA (Treponema pallidum hemagglutination assay) or TPPA (Treponema pallidum particle agglutination), serve as pathogen-specific screening tests of syphilis infection. The tests turn out positive 2-3 weeks after infection and then usually remain so for life. A negative test result after the end of the incubation period (2-3 weeks) largely rules out infection.

For confirmation in case of a positive or doubtful screening test, the Treponema pallidum antibody absorption test (FTA-ABS) is performed (= confirmatory test). If an ELISA is used as the screening test, confirmation by means of a TPHA/TPPA test and vice versa is also possible. If the confirmation test is negative, a syphilis infection is considered unlikely. If the test is positive, this indicates syphilis requiring treatment or a past or treated infection ("seroscarring"). To differentiate between these, a quantitative determination of the activity parameters must be followed.

To determine disease activity, a quantitative T. pallidum-specific IgM antibody determination or a VDRL (Venereal Disease Research Laboratory) test can be performed. IgM antibodies can be detected as early as one to two weeks after infection and should be undetectable within six to twelve months with therapy. The VDRL test is positive only after four to six weeks; a declining titer under therapy indicates successful treatment, but the antibodies may persist for life.

If syphilis is present, further diagnostics should be offered to exclude other sexually transmitted diseases.

Last updated: 10.10.2023

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