Syphilis is a bacterial sexually transmitted infection that can spread through vaginal sex, anal sex, oral sex, and pregnancy. It is treatable and curable, but without testing and treatment, it can lead to serious long-term health problems.
It has several stages, and symptoms can come and go. Some people may not notice symptoms at all. That is why routine testing, honest sexual health conversations, partner notification, and stigma-free education matter.
KISS helps users learn about syphilis and other STDs/STIs, set testing reminders, track encounters, send partner alerts, and build safer sex habits in one private app.
What is syphilis?
Syphilis is a bacterial sexually transmitted infection caused by Treponema pallidum. Infection can affect different parts of the body and can progress through stages if it is not treated.
It can spread through direct contact with a sore during vaginal, anal, or oral sex. It can also pass from a pregnant person to a baby during pregnancy, which is called congenital syphilis.
Having it does not mean someone is dirty, careless, or irresponsible. Syphilis is a health condition. Testing, treatment, prevention tools, and partner communication can help people take care of themselves and their partners without shame.
Recent syphilis statistics and infection trends
Infections have received more attention in recent years because cases increased significantly in many places, including the United States. More recent data shows some signs of progress, but it remains a major public health concern.
A few important statistics:
- WHO estimates that 8 million adults between ages 15 and 49 acquired syphilis in 2022.
- In 2024, more than 2.2 million cases of chlamydia, gonorrhea, and syphilis were reported in the United States.
- CDC reported that primary and secondary syphilis, the most infectious stages, declined in 2024 compared with 2023.
- Congenital infection increased again in 2024, with nearly 4,000 reported cases.
- CDC reported that congenital syphilis remains about 700% higher than it was a decade ago.
These numbers show why education, testing, treatment access, pregnancy screening, and partner communication still matter. The goal is not fear. The goal is better information, earlier testing, and less stigma.
How it spreads
It can spread through direct contact with a sore or infectious lesion.
Infection can spread through:
- vaginal sex
- anal sex
- oral sex
- skin-to-skin sexual contact with a sore
- pregnancy, if syphilis passes from a pregnant person to a baby
It does not spread through casual contact like hugging, sharing food, toilet seats, or everyday social contact.
Condoms and barriers can reduce the chance of transmission, but they may not fully protect areas not covered by the barrier. That is one reason testing and awareness matter.
Symptoms and stages
Syphilis can look different depending on the stage. Symptoms can also be mild, painless, or easy to miss.
Primary
Primary infection often causes a sore called a chancre. A chancre is usually firm, round, and painless. It may appear on the genitals, anus, rectum, lips, mouth, or throat depending on the exposure.
Because the sore may not hurt, someone might not notice it. The sore can also heal on its own, but that does not mean the infection is gone.
Secondary
Secondary infection can cause symptoms such as:
- rash, sometimes on the palms of the hands or soles of the feet
- fever
- swollen lymph nodes
- sore throat
- patchy hair loss
- headaches
- muscle aches
- tiredness
- sores in the mouth, vagina, anus, or rectum
These symptoms may go away even without treatment, but the infection can still remain in the body.
Latent
Latent syphilis is a stage where there may be no symptoms. A person may feel fine and not know it is still present.
Testing is important because it can stay in the body even when symptoms disappear.
Tertiary
Tertiary syphilis can happen years later if it is not treated. This stage can affect the brain, nerves, eyes, heart, blood vessels, liver, bones, joints, and other organs.
Not everyone with untreated syphilis develops tertiary syphilis, but the possible complications can be serious. Early testing and treatment can help prevent long-term damage.
Can syphilis have no symptoms?
Yes. Many people who are infected do not notice symptoms or may not recognize them.
A sore may be painless. A rash may be mistaken for something else. Symptoms may disappear without treatment. That can make syphilis easy to miss.
This is why testing matters. Testing is routine sexual health care. It is not about shame or judgment.
How testing works
Testing usually involves a blood test. If someone has an open sore, a healthcare provider may also take a swab or sample from the sore.
Testing may include:
- a blood test
- a swab or sample from a sore, if one is present
- follow-up testing after treatment, depending on provider guidance
A provider may also recommend testing for other STDs/STIs, such as HIV, chlamydia, gonorrhea, or hepatitis, depending on symptoms, sexual history, and possible exposure.
If you have oral, anal, or vaginal sex, it can be helpful to tell a healthcare provider what kinds of sex you have. That helps them recommend the right testing and care.
Syphilis treatment
Syphilis is treatable and curable with antibiotics.
Treatment depends on the stage of syphilis and a person’s medical situation. Penicillin is commonly used to treat syphilis. If someone has a penicillin allergy or another medical consideration, a healthcare provider can explain the safest option.
It is important to follow treatment instructions exactly. Recent partners may also need testing or treatment. If one person is treated but a partner is not, reinfection can happen.
Many healthcare sources recommend avoiding vaginal, anal, and oral sex until treatment is complete, sores are healed, and a healthcare provider says it is okay.
Partner notification after syphilis
If someone tests positive for syphilis, recent partners may need to know so they can get tested or treated.
Partner notification can feel uncomfortable, but it can also be a practical and caring part of sexual health. It is not about blame. It is about giving someone information that may help protect their health.
KISS supports private partner alerts so users can notify partners about a possible STI exposure with more privacy, less shame, and more control.
Long-term risks of untreated syphilis
Syphilis is treatable, but untreated syphilis can sometimes lead to serious long-term health problems.
Possible long-term risks may include:
- damage to the brain or nervous system
- vision problems or eye involvement
- hearing problems
- heart and blood vessel problems
- damage to organs
- pregnancy complications
- congenital syphilis
- stillbirth, newborn illness, or infant death in severe pregnancy-related cases
These risks are one reason testing and treatment are important. Treating syphilis can cure the infection, but some damage from late-stage syphilis may not be reversible.
Syphilis and pregnancy
Syphilis can pass from a pregnant person to a baby during pregnancy. This is called congenital syphilis.
Congenital syphilis is preventable, but it can be very serious if syphilis is not detected and treated during pregnancy. It may lead to miscarriage, stillbirth, premature birth, newborn illness, or infant death.
Because congenital syphilis has increased sharply in recent years, syphilis screening during pregnancy is especially important. Pregnant people should follow medical guidance about testing and treatment.
How to reduce syphilis risk
Syphilis prevention is not about fear or shame. It is about information, communication, testing, and access to care.
Ways to reduce risk may include:
- routine STD/STI testing
- condoms or barriers during vaginal, anal, or oral sex
- talking with partners about testing
- getting tested after a possible exposure
- getting treated if you test positive
- making sure recent partners get tested or treated
- following healthcare provider guidance before having sex again after treatment
- using testing reminders to stay on track
Different people have different bodies, partners, relationships, and sex lives. KISS is designed to support sexual health decisions without judgment.
Learn more with KISS
KISS helps users connect syphilis education with broader sexual health tools, including STD information, testing reminders, partner alerts, encounter tracking, and safer sex habits.
Users can explore our STD information guide to learn more about symptoms, testing, treatment, prevention, and sexual health statistics.
Users can also learn about common STIs and STDs, including symptoms, testing, and prevention.
For private partner communication, KISS also supports anonymous STI notification through partner alerts.
Users can also read about HIV education, testing, PrEP, PEP, and prevention.
KISS does not replace medical care
KISS is not a substitute for medical advice, diagnosis, or treatment. If you have symptoms, test positive, are pregnant, or think you may have been exposed to syphilis or another STD/STI, consider getting tested and speaking with a healthcare provider.
KISS can help users learn, track, set reminders, and communicate more privately, but medical testing and treatment should come from a qualified healthcare provider.