What Is Syphilis?
RgStudio / Getty Images
Syphilis is a sexually transmitted infection (STI) caused by a bacterium known as Treponema pallidum. The infection spreads through sexual contact and can progress through four stages if left untreated. The four stages, primary, secondary, latent, and tertiary, come with their signs and symptoms.
The bacteria that cause infection can spread throughout the body, causing different health issues. The types of syphilis include neurosyphilis, ocular syphilis, and otosyphilis. Syphilis can affect the skin and scalp, mouth, genitals, anus, throat, heart, blood vessels, liver, bones, and joints.
This article discusses the symptoms, causes, and treatment options for syphilis and the stages of infection.
RgStudio / Getty Images
Syphilis Stages and Symptoms
There are four stages of a syphilis infection. A person with untreated syphilis can gradually move from one stage to another over the course of 10 or more years.
Primary
The primary stage of syphilis typically occurs within three weeks of exposure to the bacteria. However, signs of infection can occur in as little as 10 days or take as long as 90 to develop. The site chancre is where syphilis enters the body. The signs and symptoms that develop during primary syphilis include:
Painless sores or chancres in the genital area
Swollen lymph nodes
Chancres that appear elsewhere on the body (not just in the genitals)
After three to six weeks, syphilis sores will heal independently, and the infection will progress into secondary syphilis if left untreated.
Primary syphilis chancres often go unnoticed because they are painless, small, and challenging to see if they are located somewhere within the body, such as the vagina or anus. Sometimes, they may fill with fluid, but that is not always the case.
Secondary
Secondary syphilis develops within two weeks to six months of contracting the bacteria that causes the infection. Typically, the secondary stage begins within eight weeks of a chancre developing in the primary stage.
The symptoms that develop during this stage are starkly different from those in primary syphilis and can include:
Fever
Headaches
A rough, red or reddish-brown skin rash on the palms of the hands or soles of the feet
A maculopapular rash (a combination of flat discoloration and raised bumps) can develop elsewhere on the body
Sores in the mouth, vagina, or anus
Raised and large gray or white lesions (condyloma lata)
Swollen lymph nodes
Sore throat
Patchy hair loss
Weight loss
Muscle aches
In some cases, secondary syphilis can also cause neurological symptoms to develop, such as:
Nerve palsies that can cause symptoms like pain, vertigo, or paralysis
Eyes pain or redness
Meningitis, which occurs when the protective membrane of the brain and spinal cord become inflamed
Memory difficulties
Confusion and personality changes
Like other stages of a syphilis infection, the symptoms of the secondary stage go away independently. However, the bacteria are still in the body. After this stage and its symptoms subside, if the person goes untreated, syphilis goes into latency.
Latent
The latent stage falls into two categories: early latent syphilis and late latent syphilis. If a person’s infection goes into latency within 12 months of when they contracted the syphilis bacteria, it is early latency, whereas after 12 months is the late latent stage.
Little evidence is available to determine how long the latent stage lasts. It can go on for a decade or more. During this time, a person will experience no symptoms of syphilis.
If a person experiences an early latent stage of the disease, they have a 25% chance of relapsing back into secondary syphilis and the symptoms that accompany it.
Tertiary
The fourth and final stage of syphilis is known as the tertiary stage. It is a rare phase of infection and develops anywhere between 10 and 30 years after a person first becomes infected.
When syphilis remains untreated, and a person enters the tertiary stage, they can develop symptoms and health issues that are severe and life-threatening.
Many organs and bodily systems can become damaged because of a late-stage untreated syphilis infection, including the following:
Brain
Nerves
Eyes
Heart
Blood vessels
Liver
Bones
Joints
During this time, different types of syphilis can develop depending on what area of the body the bacterial infection affects most. It is also important to note that the below types of syphilis can occur at any stage of infection.
Type | Bodily System Affected | Symptoms |
Neurosyphilis | Nervous System | Severe headache Difficulty with moving muscles Paralysis in certain parts of the body Muscle weakness and numbness Mental state changes, including personality changes, difficulty with focus, and confusion Dementia (memory issues, thinking, and decision-making problems) |
Ocular Syphilis | Visual System/Eyes | Eye pain Red eyes Floating spots in the vision Increased sensitivity to light Blurry vision Blindness |
Otosyphilis | Auditory/Vestibular system | Hearing loss Hearing a ringing, buzzing, roaring, or hissing in the ears (tinnitus) Difficulties with balance Vertigo Dizziness |
Because the symptoms of primary and secondary syphilis are easy to miss or confuse with another infection, it can be easy to experience them and not automatically think of syphilis. When the latent stage hits, there are no symptoms at all. Because of that, a person can have syphilis for many years and not realize it until they reach the tertiary stage and start developing severe health problems.
Read Next:Syphilis Is Making a Comeback. Here's What to Know About Symptoms and Prevention
What Does Syphilis Look Like?
Syphilis has many faces and will look different during each stage. During primary syphilis, a person may not notice the chancre that develops. In stage 2, or the secondary stage of syphilis, the skin rashes can become more noticeable but are often subtle.
Mucus lesions known as condyloma lata develop during stage 2. They appear as raised bumps that can become the same color or lighter than a person’s skin tone. They typically look:
Smooth on the surface
Papillated
Similar to cauliflower
The latent and tertiary stages are often unremarkable regarding how the infection looks on the skin. There are either no symptoms at all, or the infection has spread to organs and bodily systems that cause more systemic issues.
Reproduced with permission from ©DermNet New Zealand and © Dr. Richard Ashton www.dermnetnz.org 2023.
Learn More:What Does a Faint Syphilis Rash Look Like?
What Causes Syphilis?
The treponema pallidum bacteria causes syphilis. When the bacteria enter the body, it remains until treated. The bacterium can evade detection from the immune system and invade the entire body if left for too long.
How Syphilis Is Transmitted
Syphilis is a sexually transmitted infection because it spreads primarily through sexual skin-to-skin contact with someone with a syphilis sore. Pregnant people can also transmit the infection to their unborn child. The types of sexual contact responsible for the spread of syphilis include:
Genital
Anal
Who Has the Highest Risk of Developing Syphilis?
Any sexually active person can contract syphilis, but some are more at risk than others. Those most at risk are men who have sex with other men.
Others who are most at risk include:
Female sex workers
People who engage in sexual activities with sex workers
People living in lower-income countries and areas
People who engage in condomless sex practices with multiple partners
Males who are human immunodeficiency virus (HIV)-positive
Incarcerated individuals
People who engage in sexual activity while using drugs
Research shows roughly 17.7 million people were diagnosed with syphilis globally in 2012 alone. The age group most associated with the infection is those between 15 and 49. It’s estimated that 5.6 million new cases will be documented each year. More recent research established by the CDC in 2020 estimates that, in the United States alone, roughly 133,945 new cases of syphilis were reported.
Learn More:Syphilis Facts and Statistics: What You Need to Know
When Are You Most Contagious With Syphilis?
Syphilis is highly contagious but not during all four stages. When symptoms develop during the first and second stages, the infection can easily spread from partner to partner but is less likely during the third and fourth stages.
That said, passing on the infection during the late latent stage and tertiary infection is still possible. Passing on syphilis during these stages of infection does not happen often.
For How Long Are You Contagious?
Because a person typically goes through the primary, secondary, and early latency stages of syphilis within one year, the 12-month period after a person first contracts syphilis is the most contagious.
You can, however, pass on the infection during other stages. Because it’s hard to say how long a person's syphilis infection will remain latent, pinpointing exactly how long a person can pass it on is difficult.
Tests for Syphilis
Testing for syphilis is important because when left untreated, a person can pass it on to others and develop life-threatening symptoms later in life. Though spotting a new sore may be difficult, it’s best to pay attention to any changes to your genital area, mouth, and anus as best you can so that if a chancre does develop, you can get tested quickly.
If you experience any secondary syphilis symptoms but do not notice a sore, it’s still best to contact a healthcare provider to address your concerns. The symptoms are non-specific, but it is always better to be sure.
People in higher-risk populations should also get regular STI screenings regardless of symptoms. The tests used most often to diagnose syphilis are known as Treponemal tests. They are blood tests specifically designed to hunt out syphilis antibodies created by the body in response to the infection.
Types of treponemal tests include:
Treponema pallidum particle agglutination (TP-PA)
Chemiluminescence
Immunoassays
Immunoblots
Rapid treponemal assays
When a positive result comes back, a non-treponemal test may help confirm a syphilis infection. It works by detecting damage to cells caused by the syphilis bacteria. Types of non-treponemal blood tests include:
Rapid plasma reagin (RPR)
The venereal disease research laboratory test (VDRL)
Toluidine red unheated serum test
Non-treponemal tests look for reactions with antibodies in the blood to investigate how active a syphilis infection is. The negative or positive results will help healthcare providers determine if more testing is necessary or if treatment needs to begin.
If someone is exhibiting signs of neurosyphilis, they may need to undergo further testing with a cerebrospinal fluid evaluation. During this test, spinal fluid is extracted from the body and examined for signs of bacterial infection.
In some cases, reactive blood tests may help diagnose syphilis. However, they are not as efficient at determining the activity of a syphilis infection. People who have had syphilis before and are retesting for the infection may take them.
Learn More:Diagnostic Testing for Syphilis Antibodies
Treatment for Syphilis
Syphilis is a bacterial infection that requires antibiotic treatment. That said, treatment for the infection depends on the stage. One single injection dose of an antibiotic known as penicillin G Benzathine can treat primary, secondary, or early latent syphilis.
When the infection has progressed to late latent syphilis, or if a healthcare provider cannot determine how long ago a person became infected, they will require three doses of the same medication given once per week over three weeks.
The treatment for neurosyphilis, ocular syphilis, or otosyphilis is aqueous crystalline penicillin, typically administered intravenously.
If a person cannot take this specific antibiotic or has tertiary syphilis with neurological, ocular, or ear involvement, there are other antibiotic options, including:
Aqueous crystalline penicillin
Doxycycline
Tetracycline
Ceftriaxone
Syphilis is curable with the correct antibiotics course. That said, some health ailments are irreversible in people who have experienced long-term damage caused by an untreated syphilis infection.
Complications of Untreated Syphilis
Untreated syphilis can become a life-threatening infection and cause permanent damage to many organs, including the brain, heart, and eyes. One of the most notable complications if syphilis is left untreated is dementia. Other possible severe health consequences can include:
Angina (chest pain)
Aortic aneurysm (bulging of the body's largest artery)
Heart failure
Seizures
Personality changes
Chronic pain
Joint pain
Joint damage
Blindness
Meningitis
Strokes
An inability to feel pain or temperature sensations on the skin (CIPA disease)
Sexual dysfunction
Hearing loss
Incontinence
Gummatous (rubbery or gummy tumor-like masses)
Sometimes, the damage to vital organs such as the brain and heart is so severe in a syphilis infection that it can lead to death. Though it could take years for the signs of the damage to show up, it can occur if the condition remains untreated.
Learn More:What Are the Side Effects of Untreated Syphilis?
Syphilis and Pregnancy
Having syphilis while pregnant can spread the infection to the unborn child. According to the Centers for Disease Control and Prevention (CDC), people in the first and third trimesters of pregnancy should test for syphilis even if they don't suspect they have it.
People who are pregnant and are at a higher risk of syphilis should especially follow these guidelines. It is crucial to get testing and ensure you do not have syphilis while pregnant because many complications can arise, such as stillbirth or having a child die shortly after birth due to the infection.
As many as 40% of people experience the death of an infant if they give birth while they have a syphilis infection.
Congenital Syphilis
If a child is born with syphilis and survives the infection, other health complications can arise, even if they do not experience symptoms of infection. Some possible congenital issues can include:
Low birth weight
Hepatosplenomegaly (an enlarged liver and spleen)
Dental alterations
Infants may not experience the typical symptoms of syphilis, even if they are born with it. However, they do require prompt treatment, or they can experience severe health complications in the weeks following their birth, such as:
Seizures
Developmental delays
Death
The treatment for syphilis in adults is the same for infants born with the infection. Instead of an injection, infants may have to receive the drugs intravenously.
Tips for Preventing Syphilis
Preventing syphilis involves practicing safer sexual behavior and knowing your risk. Some things you can do to prevent the spread of the infection include:
Wearing condoms during every sexual encounter, including anal, oral, and vaginal sex
Always completing treatment after a syphilis diagnosis to avoid transmitting it
Getting tested regularly if you fall into a higher-risk category
Avoiding sharing needles if you partake in needle-administered drug use
Avoiding sharing sex toys with others
Outlook for Syphilis
Though syphilis can be a severe and life-threatening disease, it is curable if caught early. Because of that, many people who contract syphilis can seek adequate treatment and avoid any long-term complications.
Practicing safer sex is always crucial as is speaking to your healthcare provider regularly about STI screenings and what you can do to keep yourself safe from syphilis and other sexually transmitted infections.
