Conditions and diseases


Symptoms and causes

Symptoms and causes

What is it?

Syphilis is a sexually transmitted infection (STI) caused by the bacterium Treponema pallidum. The disease only occurs in humans. Millions of people worldwide contract the disease every year.

In developing countries, congenital syphilis is a major cause of infant mortality.


There are different stages of the disease:

  • A painless ulcer at the site of the first infection, e.g. on the genitals or near the mouth, a few weeks after contact. Usually a painless swelling of the surrounding lymph nodes also occurs. The ulcer disappears spontaneously after 4-6 weeks
  • A stage with non-itchy skin abnormalities (the soles of the feet and palms of the hands are often affected), a flu-like sensation (fever, headache, sore throat, muscle pain, malaise) and other abnormalities, a few months later. At this stage, the disease is highly contagious.
  • During the third stage (many years after infection), the central nervous system is affected with severe neurological and psychiatric symptoms. Eventually, the third stage can result in cardiovascular syphilis, affecting the heart and the large blood vessels.

By no means does everyone who goes through the first stage proceed to the second or third stage. Between stage two and three, there is an interval of several years in which there are no signs of disease, but the blood tests are positive for syphilis.

Diagnosis and treatment

Diagnosis and treatment

How is the diagnosis determined?

The disease can take many forms, often resembling other diseases. Moreover, the disease is rare in Western Europe today. For both these reasons, the diagnosis is sometimes missed.

A positive diagnosis can be obtained with a blood test that detects antibodies against the bacteria. The bacteria can also be diagnosed in the fluid from an ulcer.

Additional difficulty: due to the three-month incubation period, if the initial test result is negative, it cannot be conclusively ruled out that a syphilis infection is absent. Certainty can only be obtained with a second control test three months later, which must then also be negative.


In the early stages, syphilis is easy to treat with repeated injections of antibiotics (Penicillin G).

Treatment centres and specialisations

Treatment centres and specialisations

Latest publication date: 15/05/2024
Supervising author: Dr Ameye Filip