Syphilis: A Bacterial Infection

Syphilis is a sexually transmitted infection (STI) caused by bacteria Treponema pallidum. The bacteria penetrate through mucous membrane chafed skin. The highly infectious disease is transmitted during sexual intercourse, through blood transfusion, or from mother to fetus in the womb during pregnancy. When left untreated, syphilis can cause irreversible damage to the body tissue, nerves, and brain. Men are more vulnerable to contracting this infection than women, and it affects people aged 15 to 39 years more often. There are three stages of syphilis: primary, secondary, and tertiary. If someone has been infected with the bacteria and develops syphilis for less than a year, a single dose of penicillin is enough to cure the disease. For those who are allergic to this antibiotic, doxycycline, erythromycin, or tetracycline are commonly prescribed. For the tertiary stage of syphilis, more doses and a longer therapy course is required.


Overview of Syphilis

Syphilis is a highly contagious sexually transmitted infection (STI) that is spread primarily through vaginal, oral, and anal sex. This disease causes sores to form on the mouth, genitalia, or anus, which often go unrecognized. Any contact with a contagious lesion can result in contraction of the infection. Pregnant women with syphilis can spread the bacteria to unborn babies, a condition called congenital syphilis. Syphilis is not spread by door knobs, toilet seats, hot tubs, swimming pools, sharing clothing, or eating utensils.

Incidence and Prevalence of Syphilis

Syphilis occurs more often in men and women aged 15 to 39 years. It was once a serious public health threat because it causes serious long-term health problems like brain damage and blindness. In the 1940s, penicillin was developed and found to treat this condition. According to the CDC, the rate of syphilis has greatly declined from 1941 to 2000. There was a gradual rise from 2000 to 2006, with over 36,000 cases report in 2006.

Cause of Syphilis

The bacterium that causes syphilis is Treponema pallidum, which penetrates through the mucous membrane of chafed skin or skin tears. T. pallidum is a highly infectious microorganism that is present on a skin lesion, which develops at the inoculation site. Any contact with this lesion could result in infection. Syphilis is spread during sexual activity (anal, oral, and vaginal), through blood transfusions, or from a mother to the fetus during pregnancy.

Stages of Syphilis

There are three distinct stages of syphilis. These include:

  • Primary Stage. The primary stage starts with a sore at the site of inoculation or exposure. This lesion is called a chancre (pronounces shanker). It typically appears as a craterlike sore on the genitalia, although it can occur on other parts of the body. The disease is transmitted by direct contact with the chancre, which appears three to four weeks post-exposure and heals after one week.
  • Secondary Stage. The secondary stage develops four to ten weeks after the chancre appears. It often resembles several other illnesses and will not go away without antibiotic treatment. Symptoms and signs of this stage include fever, muscle aches, joint pain, sore throat, headache, rash on the entire body (even palms and soles), decreased appetite, patchy hair loss, and enlarged lymph nodes.
  • Tertiary Stage. The tertiary stage develops during the first or second year of the infection and is characterized by occasional episodes of secondary stage symptoms. Around one third of people with syphilis develop tertiary stage disease.

Diagnosis and Treatment

Syphilis can resemble other diseases and illnesses, so the doctor must carefully assess and evaluate the symptoms and take a medical and sexual history. The doctor will ask questions concerning the progression of the rash, the onset of the illness, and so on. Blood testing is key to diagnosis, which consists of all or any of the following:

  • RPR (rapid plasma reagent).
  • VDRL (venereal disease research laboratory).
  • FTA-ABS (fluorescent treponemal antibody absorption).
  • MHA-TP (microhemagglutination assay forT. pallidum).

Treatment involves a single injection of penicillin. People who are allergic to penicillin and not pregnant can receive oral antibiotics, such as doxycycline, erythromycin, or tetracycline. For latent stage syphilis, or those who are not sure how long they have had the infection, treatment involves three injections of penicillin, given one week apart. Those allergic to penicillin receive a long course of antibiotics by mouth. When the syphilis advances and there is brain involvement (neurosyphilis), treatment involves intravenous penicillin every four hours for two weeks. An alternative treatment is probenecid four times each day for two weeks. Pregnant women should have penicillin as well, unless an allergy exists.


After treatment, the doctor requires that an infected person does not have sexual activity until the doctor confirms by blood testing that the person is no longer contagious. This may take up to three months, so it is advisable that all sexual partners and close contacts be screened for syphilis. People treated for syphilis must have repeat blood tests at three, six, and twelve months, whereas people with neurosyphilis need repeat blood tests and spinal fluid evaluations every six months for at least three years.

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