Syphilis (Treponema pallidum)

Syphilis is a sexually transmitted infection (STI) caused by the bacterium Treponema pallidum. You can catch it by having sexual contact with someone who is infected. As the initial ulcer is usually painless, not all infected people are aware that they are infected. If left untreated, syphilis can result in serious illness or, in rare cases, death. In pregnancy, the infection can be passed to the baby resulting in congenital syphilis (CS), which may cause birth defects or stillbirth.


The first symptom consists of a painless open sore called a chancre or ulcer (although it is not always painless). This usually appears three days to three months after having sex with someone infected with syphilis. The chancre appears on the site that the bacteria entered the body. This mainly occurs on the genitals (e.g. penis, vagina), mouth, or rectum.

After the initial symptoms, a body rash and flu-like symptoms may follow. Later, untreated syphilis infection can result in serious health complications and permanent damage to the brain, heart, bones, and blood vessels. Some people infected with syphilis may not develop any symptoms for years.


Syphilis is a STI that is typically spread through anal, oral, or vaginal sex. It can be spread through direct contact with syphilis ulcers or rashes. Pregnant people can pass on the infection to their baby during pregnancy or childbirth. This is called congenital syphilis and may lead to birth defects or stillbirth.

How can congenital syphilis (CS) affect a baby?

CS can have serious and permanent health impacts on a baby. How CS affects a baby's health depends on how long the birthing parent had syphilis and if, or when, they got treatment for the infection.

CS can cause:

  • miscarriage (losing the baby during pregnancy)
  • stillbirth (a baby born dead)
  • prematurity (a baby born early)
  • low birth weight
  • death shortly after birth

Up to 40 percent of babies born to people with untreated syphilis may be stillborn, or die from the infection as a newborn.

Babies born with CS may have:

  • deformed bones
  • severe anemia (low red blood cell count)
  • enlarged liver and spleen
  • jaundice (yellowing of the skin and eyes)
  • brain and nerve problems such as blindness or deafness
  • meningitis
  • skin rashes

Syphilis can be cured with antibiotics, usually penicillin. Those infected with syphilis should inform their sexual partner(s) about their diagnosis. They also need to be tested and treated to reduce the spread of the disease.

It is important to receive treatment as soon as possible. Treatment can only kill the bacteria that cause the infection. It cannot repair the damage done. People treated for syphilis can get the infection again if they have sexual contact with someone who is infected.

If tested positive for syphilis during pregnancy, treatment is required right away during pregnancy. This is important for preventing spread to the baby. Babies who have CS need to be treated right away after birth or they can develop serious health problems. Depending on the results of a baby’s medical evaluation, they may need antibiotics in a hospital for 10 days. It is also important that babies treated for CS get follow-up care to make sure that the treatment worked.

After being diagnosed and treated for syphilis, follow-up testing with a health care provider for at least one year is required to make sure that the treatment is working.

  • The risk of becoming infected with syphilis can be reduced by practicing safer sex (e.g., using condoms/barrier methods correctly and consistently).
  • Get tested regularly if you are sexually active, especially if you have new sexual partner(s).
  • If an infection is suspected, people should not have sex until all partners are tested and treated.
  • Tell your sexual partner(s) if you have a sexually transmitted or blood borne infection (STBBI), so they can be tested and treated. This will help reduce the spread of disease.
  • People with syphilis should avoid sexual contact for 7 days after finishing treatment
  • If pregnant, a syphilis test should be done three times during pregnancy - at the first prenatal visit, again at 28-32 weeks gestation, and again at delivery. Some people may be recommended to have monthly testing during pregnancy. It is very important to test and treat for syphilis during pregnancy to reduce the risk of congenital syphilis in the baby.

Talk with a doctor or health care provider about your risk for syphilis. Have an open and honest conversation about your sexual history and testing for STIs. Your doctor can give you the best advice on any testing and treatment that you may need.

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