Syphilis is a sexually transmitted bacterial infection. It is treatable in the early stages, but without treatment, it can lead to disability, neurological disorders, and even death.

The bacterium Treponema pallidum (T. pallidum) causes syphilis. The four stages of the disease are: primary, secondary, latent, and tertiary.

The Centers for Disease Control and Prevention (CDC) noted that 43% of syphilis presentations involved men who have sex with men. However, the number of cases in heterosexual men and women is also increasing.

Syphilis is treatable with antibiotics, especially in the early stages. It does not resolve without treatment.

In this article, we explain the different stages of syphilis, whether it is curable, and how to recognize and treat it.

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Syphilis is an infection that develops due to T. pallidum bacteria. These bacteria can spread between people through direct contact with a syphilitic sore.

These sores may develop on the skin or mucous membranes of the vagina, anus, rectum, lips, or mouth.

Syphilis is most likely to spread during oral, anal, or vaginal sexual activity. People rarely pass the bacteria on through kissing.

Learn more in our dedicated sexual health hub.

The first sign is a painless sore on the genitals, rectum, mouth, or another part of the skin. Some people do not notice the sore, as it does not cause pain.

These sores resolve on their own. However, if a person does not receive treatment, the bacteria remain in the body. They can remain dormant in the body for decades before reactivating and damaging organs, including the brain.

Doctors categorize the stage of syphilis as either primary, secondary, latent, or tertiary. A variety of symptoms define each stage.

The disease can be contagious during the primary and secondary stages and, occasionally, the early latent phase. It is contagious when open lesions or sores are present. Tertiary syphilis is not contagious, but it has the most severe symptoms.

Primary symptoms

The symptoms of primary syphilis include one or more painless, firm, and round syphilitic sores or chancres. These appear 10 days to 3 months after the bacteria enter the body.

Chancres resolve within 2–6 weeks. However, without treatment, the bacteria may remain in the body.

Secondary symptoms

Without treatment, syphilis can progress to its second state. This involves more severe symptoms, including:

These symptoms may resolve a few weeks after they first appear. They might also return several times over a longer period.

Without treatment, secondary syphilis can progress to the latent and tertiary stages.

Read more about secondary syphilis.

Latent syphilis

The latent phase can last for several years. During this time, the body will harbor the disease without symptoms.

However, the T. pallidum bacteria remain dormant in the body, and there is always a risk of recurrence. Doctors still recommend treating syphilis at this stage, even if symptoms do not occur.

After the latent phase, tertiary syphilis may develop.

Tertiary syphilis, or late syphilis

Tertiary syphilis can occur 10–30 years after the onset of the infection, usually after a period of latency during which there are no symptoms. However, it may appear as soon as 2-3 years after acquisition.

At this stage, syphilis damages the following organs and systems:

  • blood vessels
  • liver
  • bones
  • joints

Gummas may also develop. These are soft tissue swellings that can occur anywhere on the body.

Heart complications

Tertiary syphilis can lead to severe cardiovascular complications. These include:

Organ damage means that tertiary syphilis can often lead to death. Treating syphilis before it reaches this stage is, therefore, critical.

Neurosyphilis

Neurosyphilis is a condition that develops when T. pallidum bacteria spreads to the nervous system. It often has links to latent and tertiary syphilis. However, it can occur at any time after the primary stage.

A person with neurosyphilis may be asymptomatic for a long time. Alternatively, symptoms might develop gradually.

Symptoms include:

Congenital syphilis

Congenital syphilis is severe and frequently life threatening. T. pallidum bacteria can transfer from a pregnant person to a fetus through the placenta and during the birth process.

Data suggests that around 40% of births to people with untreated syphilis result in early fetal or neonatal death.

Congenital syphilis can also result in preterm birth or low birth weight and infection in infants.

Other symptoms in newborns include:

  • saddle nose, in which the bridge of the nose is missing
  • fever
  • difficulty gaining weight
  • a rash of the genitals, anus, and mouth
  • small blisters on the hands and feet
  • watery nasal fluid

Older infants and young children may experience:

  • Hutchinson teeth, or abnormal, peg-shaped teeth
  • bone pain
  • vision loss
  • hearing loss
  • joint swelling
  • saber shins, bowing of the legs
  • scarring of the skin around the genitals, anus, and mouth
  • gray patches around the outer vagina and anus

Learn how to recognize different STDs here.

A doctor will perform a physical examination and ask about a person’s sexual history before conducting clinical tests to confirm syphilis.

Tests include:

  • Blood tests: These can detect a current or past infection, as antibodies to the syphilis bacteria will be present for many years.
  • Bodily fluid: A doctor can evaluate fluid from a chancre during the primary or secondary stage.
  • Cerebrospinal fluid: A doctor may collect this fluid through a spinal tap and examine it to monitor the disease’s effects on the nervous system.

If a person receives a diagnosis of syphilis, they must notify any sexual partners. Their partners should also undergo testing.

Local services are available to notify sexual partners of their potential exposure to syphilis, enable testing, and, if necessary, administer treatment.

Healthcare professionals will also recommend testing for HIV, and STIs such as gonorrhea, and chlamydia.

Many providers now offer at-home tests for syphilis.

When to receive testing

Many people with an STI will not be aware of it. Therefore, it is a good idea to talk with a doctor or request a test in the following situations:

  • after having sex without a barrier method
  • having a new sex partner
  • having multiple sex partners
  • a sexual partner receiving a diagnosis of syphilis
  • a man having sex with different men
  • symptoms of syphilis being present

Screening during pregnancy

The CDC recommends all pregnant people undergo syphilis screening during their first prenatal visit and again during the second and third trimesters, respectively.

Early diagnosis and treatment of syphilis during pregnancy reduces the risk of congenital syphilis.

Syphilis develops when T. pallidum transfer from one person to another during sexual activity.

The infection can pass from a woman to a fetus during pregnancy or to an infant during delivery. This type is called congenital syphilis.

Syphilis cannot spread through shared contact with objects, such as doorknobs, eating utensils, and toilet seats.

Sexually active people are at risk of contracting syphilis. Those most at risk include:

  • people who have sex without a barrier method
  • men who have sex with men
  • people living with HIV
  • individuals with more than one sexual partner

Syphilitic sores also increase the risk of contracting HIV.

Anyone who is worried that they might have syphilis or another sexually transmitted infection (STI) should speak to a doctor as soon as possible, as prompt treatment can cure it.

Early treatment with penicillin is important, as the disease can lead to life threatening consequences in the long term.

At a later stage, syphilis remains curable. However, a person may require a longer course of penicillin.

If nerve or organ damage occurs during the later stages of syphilis, treatment will not repair it. Treatment can, however, prevent further damage by clearing the bacteria from a person’s body.

Treatment for syphilis can be successful, particularly in the early stages.

The treatment strategy will depend on the symptoms and how long a person has harbored the bacteria. However, during the primary, secondary, or tertiary stage, people with syphilis typically receive an intramuscular injection of penicillin G benzathine.

Late latent and tertiary syphilis will typically require weekly injections for up to 3 weeks.

Neurosyphilis requires intravenous (IV) penicillin for 2 weeks to remove the bacteria from the central nervous system.

Curing the infection will prevent further damage to the body, and safe sexual practices can resume. However, treatment cannot undo any damage that has already occurred.

People with a penicillin allergy can sometimes use an alternative medication in the early stages. However, during pregnancy and in the tertiary stages, anyone with an allergy will undergo penicillin desensitization to allow for safe treatment.

Following delivery, newborn infants with syphilis should undergo antibiotic treatment.

Chills, fever, nausea, achy pain, and a headache may occur on the first day of treatment. Doctors refer to these symptoms as a Jarisch-Herxheimer reaction. It does not indicate that a person should stop treatment.

People with syphilis must avoid sexual contact until they complete all treatment and receive blood test results confirming that the disease has resolved.

It may take several months for blood tests to show that syphilis has reduced to an appropriate level. Low enough levels confirm adequate treatment.

Preventive measures to decrease the risk of syphilis include:

  • abstaining from sex
  • maintaining long term mutual monogamy with a partner who does not have syphilis
  • using a condom, although these only protect against genital sores and not those that develop elsewhere on the body
  • using a dental dam, or plastic square, during oral sex
  • avoiding sharing sex toys
  • refraining from alcohol and drugs that could potentially lead to unsafe sexual practices

Having syphilis once does not mean that a person has protection from it going forward. Even after treatment has successfully removed syphilis from a person’s body, it is possible for them to contract it again.

Syphilis is a bacterial infection that can spread through sexual intercourse. It typically presents as discolored sores. However, people may not experience symptoms for many years.

Without treatment, syphilis can progress through stages; primary, secondary, latent, and tertiary. Advanced syphilis can lead to severe complications such as organ damage.

Syphilis can transmit from a pregnant person to a fetus. This is known as congenital syphilis and can be life threatening for the baby.

The standard treatment option for syphilis is penicillin. With correct management, the infection is curable.