Syphilis Overview

Syphilis is a persistent, highly infectious STD that can have devastating consequences. It is caused by the spiral-shaped bacterium (spirochete) Treponema pallidum, which can live almost anywhere in the body and spreads rapidly. The disease progresses through four distinct stages—primary, secondary, latent, and tertiary—each of which can last for several years. Serious health complications are common and can be fatal in late-stage, or tertiary, syphilis.

Transmission of Syphilis

Syphilis is spread through vaginal, oral, and anal sex during the infection's primary, secondary, and early latent stages. The bacterium is usually transmitted by direct contact between mucous membranes of the genitals, mouth, or anus; or by broken skin coming into contact with open syphilitic sores. An infected mother can pass syphilis through the placenta to her developing fetus. Reinfection after cure is possible.

Incidence and Prevalence of Syphilis

Although worldwide incidence of syphilis decreased over the last 25 years and the disease was on the verge of being eliminated in many countries in 1998, infection rates have recently increased. According to the Centers for Disease Control and Prevention (CDC), a total of 49,903 cases of syphilis were reported in the United States in 2012. This rate is thought to represent approximately 80 percent of newly acquired infections.

Syphilis infection is the highest in women and men between the ages of 20 to 24. Men who have sex with men (MSM; i.e., gay and bisexual men) accounted for about 75 percent of the new cases reported in 2012. Syphilis incidence is higher in African Americans and Hispanics than in Caucasians. Poverty, lack of education, and lack of access to health care are associated with higher infection rates. Cases of congenital syphilis in newborns in the United States decreased from 360 in 2011 to 322 in 2012.

Signs and Symptoms of Syphilis

Many signs and symptoms of syphilis are hard to distinguish from other diseases. Manifestations vary according to the stage of the disease and the immune status of the infected person. Each of the four stages marks a change in the course of infection. If left untreated, or if treated in the late latent or tertiary stage of disease, syphilis causes irreversible neurological and cardiovascular damage.

Stages of Syphilis

Primary Syphilis

The first sign of syphilis usually appears 2 to 10 weeks following exposure. A red, oval sore, called a chancre (pronounced shanker) develops at the site where the bacteria entered the body. The lesion typically looks clean, is not pusfilled, and is often painless. It may develop into an ulcer that secretes clear mucus when disturbed.

Most chancres appear on the penis, anus, and rectum in men, and on the vulva, cervix, and between the vagina and anus (perineum) in women. Less commonly, they form on the lips, hands, or eyes. Sores in the vagina and rectum may go undetected unless seen by a physician. Swelling and hardening of lymph nodes in the inner thighs and groin is also common and may cause tenderness. Lesions usually heal without treatment within 6 weeks.

Secondary Syphilis

In this stage, the pathogen spreads through the blood to the skin, liver, joints, lymph nodes, muscles, and brain. A rash frequently appears about 6 weeks to 3 months after the chancre has healed. The rash may cover any part of the body, but tends to erupt on the palms or soles of the feet. It does not itch. Multiple painless lesions may also form in mucous membranes of the mouth and throat and on the bones and internal organs. At this time, the disease is highly infectious, because bacteria are present in the secretions from the lesions.

The rash usually heals without treatment within 2 to 6 weeks. Other symptoms may include fever, sore throat, fatigue, headache, neck ache, joint pain, malaise, and patches of hair loss. A significant number of patients do not develop symptoms at this stage of the disease.

Latent Syphilis

This asymptomatic stage occurs in two phases: early (within 1 year of infection) and late (after 1 year), and follows secondary syphilis. Late latent syphilis is noninfectious. The bacteria remain inactive in the lymph nodes and the spleen. Latency can last 3–30 years and may or may not progress to the final, or tertiary, syphilis. About 30 percent of infected people persist in a latent state.

Tertiary syphilis

The final stage, also called "late" syphilis, begins 3 or more years after infection. About 30–40 percent of infected people progress to this stage. At this stage, the person may no longer be contagious, but the bacteria reactivate, multiply, and spread throughout the body, damaging the heart, eyes, brain, nervous system, bones, and joints. Tumors may develop on skin, bone, testes, and other tissues; cardiovascular symptoms such as aortic aneurysm and aortic valve insufficiency may develop; degenerative central nervous system disease can produce dementia, tremors, loss of muscle coordination (ataxia), paralysis, and blindness. Damage is irreversible.

Syphilis Diagnosis

Primary syphilis is diagnosed when the syphilitic chancre on the genitals is observed and by reviewing the patient's sexual history. However, many patients with secondary and latent syphilis have no signs or symptoms of the disease. Blood, serum, and plasma tests, collectively called serologic tests, produce a definitive diagnosis.

The venereal disease research laboratory (VDRL) test and rapid plasma reagin (RPR) are used to detect the antibody called reagin, which is produced by the immune system's response to Treponema pallidum infection. "False negative" results may occur when these tests are performed during the first 3 to 6 weeks following infection (primary syphilis); negative results do not rule out syphilis during this time. The fluorescent treponemal antibody absorption (FTA) test is also routinely performed to detect treponemal-specific antibodies. FTA is a more sensitive test and thus a more reliable diagnostic tool during all stages of the disease.

Treatment for Syphilis

A single intramuscular injection of penicillin is the standard treatment for primary, secondary, and early latent syphilis. For those allergic to penicillin, antibiotics such as tetracycline, doxycycline, minocycline, erythromycin, and ceftriaxone may be used, though they may be less effective. Follow-up is necessary for about 1 year or until no bacteria are found in blood tests.

About 50 percent of people with primary and secondary syphilis experience immediate, temporary worsening of symptoms, including malaise, anxiety, and exacerbated lesions (called the Jarisch-Herxheimer reaction), when treatment begins.

Penicillin also can be used to treat tertiary, or late stage, syphilis, but cannot reverse damage that has occurred. Also, bacteria located in the central nervous system may not respond to penicillin during the tertiary stage, even when high doses are administered intravenously.

Syphilis Prognosis

Primary, secondary, and early latent syphilis can be treated successfully with antibiotics. Late latency (more than 1 year after the secondary stage) is difficult to treat. Tertiary syphilis has a very high mortality rate due to the far-reaching effects of the disease on the central nervous system.

Transmission of syphilis in utero can cause miscarriage and stillbirth. Infected infants often have irreversible central nervous system and multiorgan damage. Asymptomatic infants may develop inflammation of the cornea (keratitis), arthritis, deafness, and central nervous system damage later in life.

Syphilis Prevention

Any person who discovers that they have a genital lesion should regard it as potentially syphilitic, should be examined by a physician as soon as possible, and should stop all sexual activity.

The use of a condom during sexual intercourse helps prevent the spread of syphilis, but chancres can be on areas of the body that are not covered by the condom. Persons undergoing treatment should abstain from sexual activity until they are no longer contagious. Sex partners must be notified so that they can be tested and, if necessary, treated.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 10 Jun 1998

Last Modified: 13 Mar 2014