Syphilis develops in stages, and symptoms vary with each stage. But the stages may overlap, and symptoms don't always occur in the same order. You may be infected with syphilis and not notice any symptoms for years.

Primary syphilis

The first sign of syphilis is a small sore, called a chancre (SHANG-kur). The sore appears at the spot where the bacteria entered your body. While most people infected with syphilis develop only one chancre, some people develop several of them. The chancre usually develops about three weeks after exposure. Many people who have syphilis don't notice the chancre because it's usually painless, and it may be hidden within the vagina or rectum. The chancre will heal on its own within three to six weeks.

Secondary syphilis

Within a few weeks of the original chancre healing, you may experience a rash that begins on your trunk but eventually covers your entire body — even the palms of your hands and the soles of your feet. This rash is usually not itchy and may be accompanied by wart-like sores in the mouth or genital area. Some people also experience hair loss, muscle aches, a fever, sore throat and swollen lymph nodes. These signs and symptoms may disappear within a few weeks or repeatedly come and go for as long as a year.

Latent syphilis

If you aren't treated for syphilis, the disease moves from the secondary to the latent (hidden) stage, when you have no symptoms. The latent stage can last for years. Signs and symptoms may never return, or the disease may progress to the tertiary (third) stage.

Tertiary (late) syphilis

About 15 to 30 percent of people infected with syphilis who don't get treatment will develop complications known as tertiary (late) syphilis. In the late stages, the disease may damage your brain, nerves, eyes, heart, blood vessels, liver, bones and joints. These problems may occur many years after the original, untreated infection.

Congenital syphilis

Babies born to women who have syphilis can become infected through the placenta or during birth. Most newborns with congenital syphilis have no symptoms, although some experience a rash on the palms of their hands and the soles of their feet. Later symptoms may include deafness, teeth deformities and saddle nose — where the bridge of the nose collapses.

The cause of syphilis is a bacterium called Treponema pallidum. The most common route of transmission is through contact with an infected person's sore during sexual activity. The bacteria enter your body through minor cuts or abrasions in your skin or mucous membranes. Syphilis is contagious during its primary and secondary stages, and sometimes in the early latent period.

Less commonly, syphilis may spread through direct unprotected close contact with an active lesion (such as during kissing) or through an infected mother to her baby during pregnancy or childbirth (congenital syphilis).

Syphilis can't be spread by using the same toilet, bathtub, clothing or eating utensils, or from doorknobs, swimming pools or hot tubs.

Once cured, syphilis doesn't recur on its own. However, you can become reinfected if you have contact with someone's syphilis sore.

You face an increased risk of acquiring syphilis if you:

• Engage in unprotected sex
• Have sex with multiple partners
• Are a man who has sex with men
• Are infected with HIV, the virus that causes AIDS

Without treatment, syphilis can lead to damage throughout your body. Syphilis also increases the risk of HIV infection and, for women, can cause problems during pregnancy. Treatment can help prevent future damage but can't repair or reverse damage that's already occurred.

Small bumps or tumors

Called gummas, these bumps can develop on your skin, bones, liver or any other organ in the late stage of syphilis. Gummas usually disappear after treatment with antibiotics.

Neurological problems

Syphilis can cause a number of problems with your nervous system, including:

• Stroke
• Meningitis
• Hearing loss
• Visual problems
• Dementia
• Loss of pain and temperature sensations
• Sexual dysfunction in men (impotence)
• Bladder incontinence
• Sudden, lightning-like pains

Cardiovascular problems

These may include bulging (aneurysm) and inflammation of the aorta — your body's major artery — and of other blood vessels. Syphilis may also damage heart valves.

HIV infection

Adults with sexually transmitted syphilis or other genital ulcers have an estimated two- to fivefold increased risk of contracting HIV. A syphilis sore can bleed easily, providing an easy way for HIV to enter your bloodstream during sexual activity.

Pregnancy and childbirth complications

If you're pregnant, you may pass syphilis to your unborn baby. Congenital syphilis greatly increases the risk of miscarriage, stillbirth or your newborn's death within a few days after birth.