Medically Reviewed by Brunilda Nazario, MD on April 27, 2023
6 min read

Syphilis is a highly contagious disease that’s mostly spread through sexual activity, including oral and anal sex. The infected person often doesn’t know that they have the disease and passes it on to their sexual partner.

Syphilis was once a major public health threat. It can cause serious long-term problems such as arthritis, brain damage, and blindness. There wasn’t an effective treatment until the late 1940s, when the antibiotic penicillin was developed.

According to the CDC, the rate of new cases of syphilis plummeted in the 1990s. In 2000, it reached an all-time low since reporting began in 1941. But the disease has been on the increase ever since. In 2021, the rate of syphilis in the U.S. reached 51.5 cases per 100,000 people, the highest rate since 1990.

Syphilis is caused by the bacteria Treponema pallidum. You get it through direct contact with a syphilis sore on someone else’s body. This usually  happens during sexual activity, but the bacteria can also get into your body through cuts on your skin or through your mucous membranes.

Syphilis can’t be spread by toilet seats, doorknobs, swimming pools, hot tubs, bathtubs, shared clothing, or eating utensils.

Any sexually active person can get syphilis. But you’re at higher risk of getting syphilis if you:

  • Have unprotected sex
  • Have multiple sex partners
  • Have HIV
  • Are a man who has sex with men

Syphilis infections affect groups in the U.S. differently:

  • Men are more likely to get syphilis than women.
  • Black men specifically had the highest rate of syphilis in the U.S. in 2021, followed by American Indian or Alaska Native men.
  • In women, American Indian and Alaska Native people had the highest rate of syphilis in 2021.
  • Western states, Alaska, some southern states (like Arizona, New Mexico, and Arkansas), and South Dakota had higher rates of syphilis, compared to other states.
  • In 2021, 95% of reported syphilis cases were in cisgender people, while 0.1% were in transgender men, and 1.2%, were in transgender women. (The rest was unknown.)

Syphilis infection has three stages:

Early or primary syphilis. People with primary syphilis get one or more sores called chancres. They’re usually small, painless ulcers. They happen on your genitals, on your anus or rectum, or in or around your mouth between 10 and 90 days (3 weeks on average) after you’re exposed to the disease. Even if you don’t treat them, they heal without a scar within 6 weeks. But treatment will keep your disease from moving to the next stage.

Secondary syphilis. This stage begins 6 weeks to 6 months after you’re exposed. It may last 1 to 3 months. People with secondary syphilis usually get syphilis rash, a rosy "copper penny" rash on the palms of their hands and soles of their feet. They may also have different rashes on other parts of their body. These may look like rashes caused by other diseases. People may have moist, wart-like lesions in their groin, white patches on the inside of their mouth, swollen lymph glands, fever, hair loss, and weight loss. As with primary syphilis, symptoms of secondary syphilis will get better without treatment.

Tertiary syphilis. If the infection isn't treated, it may move on to a stage marked by severe problems with your heart, brain, and nerves. You could become paralyzed, blind, or deaf, or get dementia or impotence. It can even be deadly.

Other types of syphilis include:

  • Latent syphilis. The infection doesn’t have any noticeable symptoms but is still in your body.
  • Congenital syphilis. Pregnant women with the disease can spread it to their baby. It can harm the baby and even cause death.
  • Neurosyphilis. The infection can spread to your brain or spinal cord. You might get headaches, dementia, or numbness or become paralyzed. You could have a hard time controlling your muscles.

If you don’t get treatment, syphilis can have complications all over your body:

  • Small bumps. Bumps called gummas can grow on your skin, bones, or organs. They can destroy the tissue around them.
  • Nervous system problems. Syphilis can cause problems like headaches, meningitis, brain damage, paralysis, or hearing and vision loss.
  • Cardiovascular problems. The disease can damage your heart valves or cause bulging blood vessels (aneurysms) or an inflamed aorta (aortitis).
  • HIV. Syphilis can increase your chance of getting HIV.

The CDC says women should be tested for syphilis at least once during pregnancy. It’s best if they’re tested at their first prenatal visit. Depending on how long pregnant women have had syphilis, they have a high chance of stillbirth (birth of an infant who has died before delivery) or of giving birth to a baby who dies shortly after birth.

An infected baby may be born without symptoms but could have them within a few weeks if the disease isn’t treated right away. These signs and symptoms can be very serious. Untreated babies may have delays in their development, have seizures, or die.

Your doctor will need to do a physical exam. They might give you tests including:

  • Blood tests. A quick test at your doctor’s office or a public health clinic can diagnose syphilis.
  • Cerebrospinal fluid tests. If your doctor thinks you might have neurosyphilis, they’ll test fluid taken from around your spinal cord.
  • Darkfield microscopy. Syphilis bacteria are visible through a microscope in fluid taken from a skin sore or lymph node.

Syphilis is curable with quick diagnosis and treatment. But if it’s treated too late, it can permanently damage your heart and brain even after the infection is gone.

If you've had syphilis for less than a year, one dose of penicillin is usually enough to kill the infection. If you’re allergic to penicillin, you might get another antibiotic instead, like doxycycline. If you’re in a later stage of the disease, you’ll need more doses.

If you’re pregnant and allergic to penicillin, your doctor will probably have you go through a process called desensitization, which will let you take the drug safely.

Don’t have sexual contact until the infection is completely gone. Your sexual partners should also be tested and, if necessary, treated.

Some people with syphilis have an immune system reaction called a Jarisch-Herxheimer reaction several hours after their first treatment. This might include fever, chills, headache, upset stomach, rash, or joint and muscle pain. These problems usually go away within 24 hours.

You can get syphilis again after treatment kills the infection. The only way to avoid syphilis altogether is to not have anal, oral, or vaginal sex. But you can reduce your risk of syphilis infection:

  • Don’t have intimate contact with someone if you know they’re infected.
  • If you don’t know whether a sexual partner is infected, use a condom every time you have sex. Make sure you use the condom correctly. Syphilis can still spread if lesions aren't properly covered by a condom.
  • Be in a long-term, mutually monogamous relationship with someone who doesn't have syphilis.

If you are in a relationship with someone who has syphilis, you're at risk as well. You may need to get treatment based on your specific case. Talk to your doctor to figure out the best way to treat or prevent a syphilis infection.