Syphilis is a sexually transmitted infection caused by the spirochete bacteria Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact however it may also be transmitted from mother to fetus during pregnancy or at birth resulting in congenital syphilis.


Other human diseases caused by related Treponema pallidum include yaws (subspecies pertenue), pinta (subspecies carateum) and bejel (subspecies endemicum).


The signs and symptoms of syphilis vary depending in which of the three stages it presents (primary, secondary, and latent). The primary stage classically presents with a single chancre (a firm, painless, non-itchy skin ulceration), secondary syphilis with a diffuse rash which frequently involves the palms of the hands and soles of the feet, and latent syphilis with little to no symptoms.


It has however been known as "the great imitator" due to its frequent atypical presentations. Diagnosis is usually via blood tests however the bacteria can also be visualized under a microscope. Syphilis can be effectively treated with antibiotics, specifically intramuscular penicillin G and in those who are allergic ceftriaxone is recommended.


Syphilis is believed to have infected 12 million people worldwide in 1999, with greater than 90% of cases in the developing world. After decreasing dramatically since the widespread availability of penicillin in 1940s, rates of infection have increased since the turn of the millennium in many countries often in combination with human immunodeficiency virus (HIV).


This has been attributed partly to unsafe sexual practices among men who have sex with men, increased promiscuity, prostitution and decreasing use of barrier protection.


Syphilis may progress through 3 distinct stages. Sometimes not all 3 may be evident. 


  • Primary phase: The primary phase usually starts with a sore at the site of infection. The sore or lesion is called a chancre (pronounced shanker). This sore usually appears as a craterlike lesion on the male or female genitals, although any part of the body is at risk. Anyone who touches an infected sore can transmit the infection. This initial lesion develops 3-4 weeks after infection and heals spontaneously after 1 week. Though the sore goes away, the disease does not. It progresses into the secondary phase. 


  • Secondary phase: The secondary phase may develop 4-10 weeks after the chancre. This phase has many symptoms, which is why syphilis is called the great pretender. It may look like a number of other illnesses. This phase of syphilis can go away without treatment, but the disease then enters the third phase.


These are the most frequently reported symptoms of the secondary phase: 

  1. Fever.
  2. Joint pain.
  3. Muscle aches.
  4. Sore throat.
  5. Flulike symptoms.
  6. Whole-body rash (usually involving the palms and soles).
  7. Headache.
  8. Decreased appetite.
  9. Patchy hair loss.
  10. Swollen lymph nodes.


  • Latent (dormant) phase: The early latent phase (first 1-2 years) is characterized by occasional relapses back to symptoms of the secondary phase of syphilis. More than 2 years after the start of the latent phase, you may have no symptoms and are generally not infectious. However, you can still transmit the infection from mother to fetus or through blood transfusions. 
  1. About a third of people with latent syphilis will progress after many years (or decades) into tertiary syphilis. During this phase, the heart, brain, skin, and bones are at risk. Luckily, with the advent of penicillin, this phase is very rarely seen today. 
  2. Congenital syphilis occurs after a fetus is infected in the womb. This form of syphilis causes teeth abnormalities, bone problems, liver/spleen/kidney enlargement, brain infection, failure to thrive/poor growth, swollen lymph nodes, yellow skin (jaundice), low blood counts, and skin rashes.


Syphilis is caused by the bacterium Treponema pallidum.




Transmission of the bacteria usually occurs during vaginal, anal, or oral sex.


The syphilis bacteria are passed from person to person through direct contact with:


  • The open sore (chancre) that appears during the primary stage.
  • Mucous membrane or other sores during the secondary stage and sometimes during the latent stage.
  • Sores mainly occur on the external genitals, vagina, anus, or rectum. Sores can also occur on the lips and in or around the mouth. The bacteria most commonly enter the body through mucous membranes, usually in the area around the genitals and urinary system.
  • In rare cases, syphilis enters the body through openings in the skin, such as cuts and scrapes, or even through wet kisses, if the infected person has a sore on the mouth or lips. Syphilis may also be transmitted by using a needle previously used by an infected person.
  • Syphilis can be transmitted through a blood transfusion. But this is very rare because all donated blood in the United States and Canada is screened for some sexually transmitted diseases (STDs). And syphilis bacteria cannot survive more than 24 to 48 hours in blood stored using modern blood-banking methods.
  • A pregnant woman with syphilis can pass the disease through the placenta and infect her baby any time during pregnancy or delivery (congenital syphilis).


Syphilis cannot be spread through casual contact with toilet seats, door knobs, swimming pools, hot tubs, bathtubs, shared clothing, or eating utensils.


Having been infected with syphilis in the past does not usually protect a person from becoming infected again.


Incubation period


An incubation period is the time between exposure to a disease and the first symptom. A skin sore called a chancre is the first symptom of sexually transmitted syphilis. A chancre usually appears between 3 weeks and 3 months after a person has been infected with syphilis.


Contagious period


A person with syphilis can easily pass the disease (is contagious) to physically intimate partners when primary- or secondary-stage sores are present. But the person may be contagious for years, off and on, and is always contagious whenever an open sore or skin rash from syphilis is present.


Syphilis is treated with penicillin, administered by injection. Other antibiotics can be used for patients allergic to penicillin.


A small percentage of patients do not respond to the usual doses of penicillin. Therefore, it is important that patients have periodic repeat blood tests to make sure that the infectious agent has been completely destroyed and there is no further evidence of the disease.


In all stages of syphilis, proper treatment will cure the disease, but in late syphilis, damage already done to body organs cannot be reversed.


Prevention of Syphilis


Patients with infectious syphilis should abstain from sexual activity until rendered noninfectious by antibiotic therapy.


Talk openly with your partner about STDs, HIV, and hepatitis B infection, and the use of contraception. All sexually active persons should consider using latex condoms to prevent STDs and HIV infection, even if they are using another form of contraception.


Latex condoms used consistently and correctly are an effective means for preventing disease (and pregnancy). Since latent condoms protect covered parts only, the exposed parts should be washed with soap and water as soon after contact as possible. This applies to men and women.

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