WHAT IS SYPHILIS?
Syphilis is a sexually transmitted
infection (STI), once responsible for devastating epidemics. It is caused
by a bacterium called Treponema pallidum. The rate of primary
and secondary syphilis in the United States declined by 89.2 percent
from 1990 to 2000. The number of cases rose, however, from 5,979 in
2000 to 6,103 in 2001. The U.S. Centers for Disease Control and Prevention
reported in November 2002 that this was the first increase since 1990.
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,
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.
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
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.
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
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
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
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
- Skin ulcers
- 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.
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
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
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
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
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
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.
FOR MORE INFORMATION
National STD and AIDS Hotline
1-800-227-8922 or 1-800-342-2437 (24 hours a day, 7 days a week)
National Institute of Allergy and Infectious Diseases
National Institutes of Health
31 Center Drive, MSC 2520
Bethesda, MD 20892-2520
National Library of Medicine
8600 Rockville Pike
Bethesda, MD 20894
Centers for Disease Control and Prevention
1600 Clifton Road
Atlanta, GA 30333
American Social Health Association
P.O. Box 13827
Research Triangle Park, NC 27709-9940
NIAID is a component of the National Institutes of Health
(NIH), which is an agency of the Department of Health and Human Services.
NIAID supports basic and applied research to prevent, diagnose, and
treat infectious and immune-mediated illnesses, including HIV/AIDS
and other sexually transmitted diseases, illness from potential agents
of bioterrorism, tuberculosis, malaria, autoimmune disorders, asthma
News releases, fact sheets and other NIAID-related
materials are available on the NIAID Web site at http://www.niaid.nih.gov.
Office of Communications and Public Liaison
National Institute of Allergy and Infectious Diseases
National Institutes of Health
Bethesda, MD 20892
Last Updated November 21, 2003 (alt)