What is Syphilis?

Syphilis is a sexually transmitted or congenital infection caused by the bacterium Treponema pallidum. Although it begins as a genital infection, it becomes a systemic disease in the second (secondary syphilis), third (tertiary syphilis) or fourth stage (quaternary syphilis) and can affect most organs of the body including the bones and joints, liver, heart and brain.

Statistics on Syphilis

Syphilis is found worldwide and is still the third most common sexually transmitted bacterial infection in the United States despite being easily treatable. Almost 50, 000 new cases are reported each year in the United States, although the actual incidence is likely to be higher as not all cases are necessarily reported. Syphilis tends to affect men and women betwen 15 and 40 years of age with the highest rates in sexually active adults between 20-29 years of age. The incidence of syphilis has fortunately tended to decrease since the introduction of penicillin therapy and screening methods. However, in some groups such as homosexual men, the rates continue to increase. Periods of high illegal drugs use also correspond with higher rates of syphilis due to risk taking behaviour and needlestick transmission.

Men traditionally have higher rates of syphilis infection despite higher levels of screening than women. There are approximately 4.7 cases of primary and secondary syphilis per 100,000 men in the United States each year (2004 statistics). In particular, homosexual men are at high risk. A study conducted in 2004 showed approximately 64% of all adult primary and secondary syphilis cases were among men who have sex with men.

Women in general have lower rates of syphilis infection than men. In the United States there are approximately 0.9 cases per 100,000 women (2004 statistics). Fortunately these rates have continued to decrease over recent years.

Children: Most syphilis in children is congenital which occurs due to transmission of bacteria across the placenta from infected mothers. The risk of transmission to the fetus is very high particualrly in the earlier stages of the mother’s disease. The effects of congenital infection are usually apparent within 2-6 weeks after birth and signs of late syphilis develop beyond two years of age.

Risk Factors for Syphilis

Syphilis is an infectious disease caused by a bacteria Treponema pallidum, which penetrates broken skin or mucous membranes.

  • Transmission occurs most frequently by sexual contact- People who commonly engage in unprotected sex, sex workers, IV drug users and health care workers are at increased risk.
  • Syphilis can also be transmitted to the fetus during any stage in pregnancy.

Progression of Syphilis

The bacteria enters the body through breaches in epithelium (lining of cells).There are 4 main stages of disease and congenital syphilis which is viewed separately:

  1. Primary: between 10 and 90 days after infection. The primary lesion (called a chancre) develops at the site of entry of bacteria on the penis, cervix, vagina wall or anus. This starts as a lump and later bcomes an ulcer. This primary lesion heals spontaneously within 2-3 weeks but by this stage the bacteria has already spread through the bloodstream.
  2. Secondary: 4-10 weeks after the appearance of the primary lesion there are systemic symptoms such as fever, malaise, characteristic rash, arthralgia (pain in joints) and generalised lymphadenopathy. In pregnant women, untreated early syphilis will result in fetal infection in over 70% of cases and stillbirth in up to 30%. The chancre and rash are highly infectious.
  3. Latent: In about 20% of individuals who do not undergo treatment, the disease may recur for a period of up to 2 years; and
  4. Tertiary: (also called late benign syphilis). This late form of syphilis can cause destruction of virtually any organ in the body. Granulomas (gummas) are found in bone, skin and other tissues. The heart and blood vessels, and central nervous system are usually the most severely affected (called cardiovascualr syphilis and neurosyphilis respectively).

Congenital syphilis:
Symptoms start to appear in the 2nd to 6th week after birth including nasal discharge, lesions of the skin and mucous membranes and failure to thrive. Signs of late syphilis appear after 2 years of age and affect developing structures particularly teeth and long bones.

Symptoms of Syphilis

Sometimes syphilis is hard to diagnose. Your doctor will ask you questions about:

  • Sexual history – Number of partners, previous STDs etc.
  • Social history – Drugs use and risky behaviour.
  • In children history of syphilis in mother, exposure to syphilis and blood products is very important.
  • Symptoms and presenting complaints.

General symptoms of each different stage are listed below:

  • Primary: Chancre lesion- rounded, elevated lump that ulcerates and dissappears after a few weeks. In men the chancre appears on the penis or scrotum and in women the chancre is found on the vulva or cervix.
  • Secondary: General flu-like symptoms (fever, sore throat, malaise, arthralgia) and widespread rash. een felt.
  • Latent: No symptoms but patients may recall previous symptoms of syphilis.
  • Tertiary: (also called late benign syphilis) is slowly progressive. If the cardiovascular system is involved- shortness of breath, ankle swelling, palpitations, or chest pain. If neurosyphilis- difficulty walking, weakness and dementia (loss of memory).
  • Congenital syphilis: Nasal discharge, lesions on the skin and mucous membranes and failure to thrive (slow growth) in 2-6 weeks following birth. Late congenital syphilis occurs after 2 years.>

Clinical Examination of Syphilis

The doctor will perform a careful genital examination looking for a chancre lesion and enlarged lymph nodes. The skin will be examined for evidence of rash found in secondary syphilis or ulcerating lesions of tertiary syphilis. A thorough neurological and cardiovscular examination will be performed.

How is Syphilis Diagnosed?

FBC may reveal an elevated WCC count or anaemia due to chronic infection in the secondary stage. Elevated ESR may also be seen. More specific investigations include taking swabs of lesions to identify the bug and special blood tests looking for antibodies (agents that fight infection) against Treponema. Lumbar puncture, CXR and echocardiogram (looking at the heart) may be performed in later stages of the disease.

Prognosis of Syphilis

Prognosis depends on the stage at which infection is treated. Early and early latent syphilis have a good prognosis because no irreversible damage has occurred yet. If left untreated approximately one third will progress to tertiary syphilis which is characterised typically by irreversible damage. Damage due to cardiovascular and neurosyphilis will be halted with treatment, but not reversed.

How is Syphilis Treated?

Once the diagnosis is confirmed early infection tends to respond well to antibiotic treatment with specific types of penicillins. The duration of treatment varies depending on which type of penicillin is used, your history of allergies and the severity of the disease. Late stage disease (tertiary syphilis) requires specialist treatment and antibiotics are given intravenously whilst you are an in-patient in hospital. For treatment of early disease, you should avoid sexual contact until the initial lesions are completely healed. All sexual partners within the last three months should be told to get tested. They are often treated with similar drugs even if blood tests are negative due to the possible severity of the disease. Babies of current or previously infected mothers need to be investigated and treated by specialists.

More information

Sexually transmitted infections (STIs)
For more information on different types of sexually transmitted infections, prevention of STIs, treatments and effects on fertility, see Sexually transmitted infections (STIs).


Syphilis References

  1. Commonwealth Department of Health and Aging, Communicable Diseases in Australia, National Notifiable Diseases Surveillance System, 2006.
  2. Cotran RS, Kumar V, Collins T. Robbins Pathological Basis of Disease Sixth Ed. WB Saunders Company 1999.
  3. Fairly C, Hocking J, Medland N, Syphilis: back on the rise, but not unstoppable, MJA 2005; 183 (4): 172-173.
  4. Hicks C, Pathophysiology and natural history of syphilis, UpToDate, 2006.
  5. Kumar P, Clark M. Clinical Medicine. Fourth Ed. WB Saunders, 2002.
  6. Longmore, Wilkinson, Rajagopalan. Oxford Handbook of Clinical Medicine. Sixth Ed. Oxford University Press, 2004.
  7. Liu P, Euerle B, Syphilis, eMedicine, Web MD, 2006. Availale [online] from URL:
  8. Murray PR., Rosenthal KS., Kobayashi GS., Pfaller MA., Medical Microbiology 3rd Ed., Mosby 1998.
  9. Therapeutic Guidelines: Antibiotic Version 12. Therapeutic Guidelines Limited, 2003.

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