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Syphilis is a sexually-transmitted disease caused by the spirochete (an elongated, spiral-shaped bacterium) Treponema pallidum. This dreadful disease can lead to insanity or death and once caused terrible epidemics. The symptoms can resemble those of other diseases, which can make diagnosis difficult. In 1996, there were over 11,000 cases reported to the Centers for Disease Control in the U.S.; in that same year, the World Health Organization estimated that there were 11 million cases worldwide.

While the disease is curable, its slow and sometimes asymptomatic onset may cause people to put off seeking treatment. This is doubly worrisome because medical research indicates that if a person is silently infected with syphilis, he or she is much more likely to catch and pass on HIV, the virus that causes AIDS.

Disease Symptoms

Syphilis is characterized by four stages:

Primary Stage
  • occurs 10-100 days after infection.

  • is characterized by the appearance of one or more chancres (a red, bloodless, painless ulcer less than 1 cm in diameter, pronounced "shan-ker").

    These appear on the genitalia (and can be inside the vagina in women and can go unnoticed). A chancre may appear elsewhere on the body; if so, it can become inflamed and/or produce pus. A chancre lasts 3-6 weeks and heals without treament, leaving a small scar.

  • causes swollen lymph nodes near the site of a chancre.

  • is contagious.
Secondary Stage
  • is characterized by rashlike skin lesions that can cover part or all of the body. The lesions are painless (unless they get a secondary infection) and appears 1-6 months after the appearance of the chancre. They can resemble warts, pustules, or ulcers. Left untreated, they heal in 2-12 weeks without scarring.

  • also causes fever, sore throat, weakness, weight loss, swelling of the lymph nodes, and loss of the eyelashes and/or part of the eyebrows.

  • can turn into meningovascular syphilis, a secondary form characterized by inflammation of the covering of the brain and spinal cord (aseptic meningitis) and/or changes in the vascular structure of the brain.

  • is contagious.
Latent Syphilis ("Hidden Stage")
  • the infected person appears to have recovered and is usually symptom-free.

  • it lasts from 1-46 years (2-20 years is most common)

  • it can be interrupted by relapses to secondary stage syphilis; 25% of infectees have relapses, usually in the 1st year of latency (but relapses can occur up to 4 years after latency starts).

  • it is not contact infectious, except during a relapse; however, children born to latent infectees may still be congenitally infected.
Tertiary Syphilis ("Late Stage")

A person who has been infected with syphilis does not acquire immunity to it (more on this later).

If a woman with syphilis gets pregnant, her child may be born with congenital syphilis. 40% of infected fetuses die before birth; newborns suffer from secondary-stage syphilis and enter the latent stage if they survive their first year.

Diagnosis and Treatment

Doctors typically first diagnose syphilis by recognizing the symptoms outlined above. A physician may confirm his or her diagnosis by taking a scraping from a chancre and examining it under a darkfield microscope to look for the spirochetes themselves.

However, this method may yield falsely negative results for up to three months after a person has been infected. A more common (and much more reliable) method of diagnosis is to give the patient one of two blood tests: the VDRL (Venereal Disease Research Laboratory) test and the RPR (Rapid Plasma Reagin) test. However, people who are infected with other sorts of viruses or who have autoimmune disorders may get a false positive from either of the tests.

Thus, if a person gets a positive result from a blood test, his or her physician will typically order another test to confirm the results. Confirmatory tests include the fluorescent treponemal antibody-absorption (FTA-ABS) test (which can accurately detect 70-90% percent of infections) and the T. pallidum hemagglutination assay (TPHA). These tests check for the presence of the transient antibodies a person's body generates against the infection; these antibodies don't last long enough to confer future immunity to the disease.

People with late-stage syphilis may have to undergo a painful spinal tap to see if the bacteria have infected their nervous system.

Syphilis can be cured with antibiotics, typically penicillin injections (though other drugs can be used if the person is allergic to penicillin). People diagnosed with the disease are usually given later blood tests to make sure the infection is gone.

The bacterium is fairly fragile and doesn't last long outside the human body, so sexual contact is the main way people catch the disease. Using a condom during sex can reduce the risk of transmission.

For more information ....

Those brave souls among you who seek pictures of syphilis infections may browse the offerings at http://www.hkmj.org.hk/skin/syphilis.htm.


This writeup is based on work I wrote for the science dictionary at http://biotech.icmb.utexas.edu/. Other information was gleaned from http://www.metrokc.gov/health/apu/std/syphilis.htm, http://www.ama-assn.org/special/std/support/educate/stdsyph.htm, and http://www.rlc.dcccd.edu/MATHSCI/reynolds/history/syphilis/history.htm