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What is syphilis?

Syphilis is a sexually transmitted infection (STI), once responsible for devastating epidemics. It is caused by a bacterium called Treponema pallidum.
Of increasing concern is the fact that syphilis increases by 3- to 5-fold the risk of transmitting and acquiring HIV (human immunodeficiency virus), the virus that causes AIDS (acquired immunodeficiency syndrome).
How is syphilis transmitted?
The syphilis bacterium is very fragile, and the infection is almost always transmitted by sexual contact with an infected person. The bacterium spreads from the initial ulcer (sore) of an infected person to the skin or mucous membranes (linings) of the genital area, mouth, or anus of an uninfected sexual partner. It also can pass through broken skin on other parts of the body.
In addition, a pregnant woman with syphilis can pass T. pallidum to her unborn child, who may be born with serious mental and physical problems as a result of this infection.
What are the symptoms of syphilis?
The initial infection causes an ulcer at the site of infection. The bacteria, however, move throughout the body, damaging many organs over time. Medical experts describe the course of the disease by dividing it into four stages-primary, secondary, latent, and tertiary (late). An infected person who has not been treated may infect others during the first two stages, which usually last 1 to 2 years. In its late stages, untreated syphilis, although not contagious, can cause serious heart abnormalities, mental disorders, blindness, other neurologic problems, and death.
Primary syphilis
The first symptom of primary syphilis is an ulcer called a chancre ("shan-ker"). The chancre can appear within 10 days to 3 months after exposure, but it generally appears within 2 to 6 weeks. Because the chancre may be painless and may occur inside the body, the infected person might not notice it. It usually is found on the part of the body exposed to the infected partner's ulcer, such as the penis, vulva, or vagina. A chancre also can develop on the cervix, tongue, lips, or other parts of the body. The chancre disappears within a few weeks whether or not a person is treated. If not treated during the primary stage, about one-third of people will go on to the chronic stages.
Secondary syphilis
A skin rash, with brown sores about the size of a penny, often marks this chronic stage of syphilis. The rash appears anywhere from 3 to 6 weeks after the chancre appears. While the rash may cover the whole body or appear only in a few areas, it is almost always on the palms of the hands and soles of the feet.
Because active bacteria are present in the sores, any physical contact-sexual or nonsexual-with the broken skin of an infected person may spread the infection at this stage. The rash usually heals within several weeks or months.
Other symptoms also may occur, such as mild fever, fatigue, headache, sore throat, patchy hair loss, and swollen lymph glands throughout the body. These symptoms may be very mild and, like the chancre of primary syphilis, will disappear without treatment. The signs of secondary syphilis may come and go over the next 1 to 2 years of the disease.
Latent syphilis
If untreated, syphilis may lapse into a latent stage during which the disease is no longer contagious and no symptoms are present. Many people who are not treated will suffer from no further signs and symptoms of the disease.

Tertiary syphilis
Approximately one-third of people who have had secondary syphilis go on to develop the complications of late, or tertiary, syphilis, in which the bacteria damage the heart, eyes, brain, nervous system, bones, joints, or almost any other part of the body. This stage can last for years, or even for decades. Late syphilis can result in mental illness, blindness, other neurologic problems, heart disease, and death.
How is syphilis diagnosed?
Syphilis is sometimes called "the great imitator" because its early symptoms are similar to those of many other diseases. Sexually active people should consult a doctor or other health care worker about any rash or sore in the genital area. Those who have been treated for another STI, such as gonorrhea, should be tested to be sure they do not also have syphilis.
There are three ways to diagnose syphilis:

  • recognizing the signs and symptoms
  • examining blood samples
  • identifying syphilis bacteria under a microscope

The doctor usually uses all these approaches to diagnose syphilis and decide upon the stage of infection.
Blood tests also provide evidence of infection, although they may give false-negative results (not show signs of an infection despite its presence) for up to 3 months after infection. False-positive tests (showing signs of an infection when it is not present) also can occur. Therefore, two blood tests are usually used. Interpretation of blood tests for syphilis can be difficult, and repeated tests are sometimes necessary to confirm the diagnosis.
How is syphilis treated?
Unfortunately, the early symptoms of syphilis can be very mild, and many people do not seek treatment when they first become infected.

Doctors usually treat patients with syphilis with penicillin, given by injection. They use other antibiotics for patients allergic to penicillin. A person usually can no longer transmit syphilis 24 hours after starting treatment. Some people, however, do not respond to the usual doses of penicillin. Therefore, it is important that people being treated for syphilis have periodic blood tests to check that the infectious agent has been completely destroyed
People with neurosyphilis may need to be retested for up to 2 years after treatment. In all stages of syphilis, proper treatment will cure the disease. But in late syphilis, damage already done to body organs cannot be reversed.
What are the effects of syphilis in pregnant women?
A pregnant woman with untreated, active syphilis is likely to pass the infection to her unborn child. In addition, miscarriage may occur in as many as 25 to 50 percent of women acutely infected with syphilis during pregnancy. Between 40 to 70 percent of women with active syphilis will give birth to a syphilis-infected infant.
Some infants with congenital syphilis may have symptoms at birth, but most develop symptoms between 2 weeks and 3 months later. These symptoms may include

  • skin ulcers
  • rashes
  • fever
  • weakened or hoarse crying sounds
  • swollen liver and spleen
  • yellowish skin (jaundice)
  • anemia (low red blood cell count)
  • various deformities

People who care for infants with congenital syphilis must use special cautions because the moist sores are infectious.

Rarely, the symptoms of syphilis go undetected in infants. As infected infants become older children and teenagers, they may develop the symptoms of late-stage syphilis, including damage to their bones, teeth, eyes, ears, and brains.
Testing recommendations for pregnant females
All pregnant women should be routinely screened for syphilis infection during the first prenatal visit.

Rescreen pregnant women who are at high risk for syphilis, live in urban areas, or are previously untested should be screened again early in the third trimester (at approximately 28 weeks' gestation) and at delivery.

Risk factors include: having had more than one sex partners in the previous six months, evaluation or treatment for an STD and/or other behaviors that place them at an increased risk for an STD.

Infants should not be discharged from the hospital unless the syphilis serologic status of the mother has been determined at least one time during pregnancy and preferably again at  delivery.

Any woman who delivers a stillborn infant should be tested for syphilis regardless of risks or residence.
Can syphilis cause other complications?
Syphilis bacteria frequently invade the nervous system during the early stages of infection. Approximately 3 to 7 percent of persons with untreated syphilis develop neurosyphilis, a sometimes serious disorder of the nervous system. In some instances, the time from infection to developing neurosyphilis may be up to 20 years.

Some people with neurosyphilis never develop any symptoms. Others may have headache, stiff neck, and fever that result from an inflammation of the lining of the brain. Some people develop seizures. People whose blood vessels are affected may develop symptoms of stroke with numbness, weakness, or visual problems. Neurosyphilis may be more difficult to treat, and its course may be different, in people with HIV infection or AIDS.
How can syphilis be prevented?
 The open sores of syphilis may be visible and infectious during the active stages of infection. Any contact with these infectious sores and other infected tissues and body fluids must be avoided to prevent spread of the disease. As with many other STIs, using latex male condoms properly during sexual intercourse may give some protection from the disease.
Screening and treatment of infected individuals, or secondary prevention, is one of the few options for preventing the advanced stages of the disease. Testing and treatment early in pregnancy are the best ways to prevent syphilis in infants and should be a routine part of prenatal care.
What research is going on?
Developing better ways to diagnose and treat syphilis is an important research goal of scientists supported by the National Institute of Allergy and Infectious Diseases (NIAID). New tests are being developed that may provide better ways to diagnose syphilis and define the stage of infection.
In an effort to stem the spread of syphilis, scientists are conducting research on the development of a vaccine. Molecular biologists are learning more about the various surface components of the syphilis bacterium that stimulate the immune system to respond to the invading organism. This knowledge will pave the way for development of an effective vaccine that can ultimately prevent this STD.
A high priority for researchers is developing a diagnostic test that does not require a blood sample. Saliva and urine are being evaluated to see whether they would work as well as blood. Researchers also are trying to develop other diagnostic tests for detecting infection in babies.
Another high research priority is the development of a safe, effective single-dose oral antibiotic therapy for syphilis. Many patients do not like getting an injection for treatment, and about 10 percent of the general population is allergic to penicillin.
The genome of the bacterium that causes syphilis has been sequenced through NIAID-funded research. The DNA sequence represents an encyclopedia of information about the bacterium. Clues as to how to diagnose, treat, and vaccinate against syphilis have been identified and are fueling intensive research efforts on this ancient but intractable disease.