This page is general health information, not medical advice. It cannot tell you whether you have an infection. A clinician can, and the testing options on this site are a good place to start.

Syphilis is a bacterial infection that is easy to miss and straightforward to treat. Many people never notice the first sign. The rash that comes later can be faint. A blood test is the only reliable way to find out.

The good news is that syphilis is curable with treatment from a clinician. This guide covers what the bacterium does, the stages and what they can look like, how the blood tests work, how treatment and follow-up are handled, and what the numbers look like in Chicago and Illinois.

It is written for people of every gender and orientation. Anyone who is sexually active can get syphilis, and getting tested is a routine part of health care.

The short answer: is syphilis curable?

Yes. The CDC STI Treatment Guidelines (2021) list penicillin, given by a clinician, as the preferred treatment for syphilis at every stage. Syphilis is a bacterial infection, and bacterial STIs can be cured with the right treatment.

Two cautions come with that answer. First, treatment stops the infection but cannot reverse damage that has already happened, according to the CDC. That is one reason earlier testing matters. Second, being cured does not make anyone immune. A person can get syphilis again, so retesting after new exposures is part of good care.

The specific medicine, the number of visits and the plan for each person are decisions for a clinician. This page does not cover doses or schedules.

The organism behind syphilis

You asked for the science, so here is the biology in plain terms. Syphilis is caused by a spiral-shaped bacterium called Treponema pallidum. It is thin and delicate, and it does not survive long outside the human body. The CDC notes that it is not spread through everyday contact such as toilet seats, doorknobs or shared dishes.

The bacterium passes through direct contact with a syphilis sore during vaginal, anal or oral sex. It can also pass from a pregnant person to the baby, which is called congenital syphilis.

Two features of this organism explain why testing works the way it does.

It cannot be grown in a routine lab dish. Labs do not usually culture it the way they do for some other infections. Diagnosis relies mostly on blood tests that look for the body's immune response.
It is good at hiding from the immune system. Research suggests the bacterium has few proteins on its outer surface, which may help it persist in the body for years. This is one observation scientists use to explain why untreated infection can go quiet and then return in a later stage.

Syphilis symptoms by stage

The CDC describes syphilis in stages. Not everyone moves through each stage in a visible way, and the signs can be subtle. Only a test can say whether an infection is present.

Primary stage: a sore, often painless

The first sign is usually a single sore called a chancre. The CDC says it often appears about three weeks after exposure, though the range is wide. It is typically firm, round and painless.

Because it does not hurt, it is easy to overlook. It can also appear inside the vagina, in the rectum or in the mouth, where a person may not see it. The sore heals on its own in a few weeks, even without treatment. Healing does not mean the infection is gone.

Secondary stage: syphilis rash and other body-wide signs

Weeks to months later, the infection can show up across the body. The syphilis rash is the best-known sign. The CDC describes it as rough, red or reddish-brown spots that often appear on the palms of the hands and the soles of the feet, but it can show up on other parts of the body too. It usually does not itch, and it can be so faint that people do not notice it.

Other secondary syphilis symptoms the CDC lists include:

Fever
Swollen lymph glands
Sore throat
Patchy hair loss
Headaches and muscle aches
Tiredness and weight loss
Moist, wart-like patches in warm areas such as the groin or mouth

These signs can also come from many other conditions, so they do not point to syphilis on their own. They clear up without treatment too, which again does not mean the infection has gone.

Latent stage: no signs at all

After the secondary stage, the infection can enter a latent period with no symptoms. The CDC says this can last for years. A person in this stage can feel completely well, and a blood test is the only way to detect it.

Tertiary stage: late complications

Without treatment, some people go on to develop serious problems affecting the heart, blood vessels, brain and other organs. The CDC says this can appear 10 to 30 years after infection began. It is far less common than the earlier stages, and it is the outcome that regular testing and treatment are meant to prevent.

Infection of the nervous system, eyes and ears

The CDC notes that syphilis can affect the nervous system (neurosyphilis), the eyes (ocular syphilis) or the ears (otosyphilis) at any stage. Changes in vision, hearing loss, ringing in the ears, severe headache or changes in thinking or balance are reasons to see a clinician promptly. The sooner a clinician evaluates these, the better.

Why the national rise matters

The CDC's national surveillance reports show that syphilis has risen sharply in the United States over the past several years, including congenital syphilis. In a disease that was once close to being eliminated, that is a shift public health agencies take seriously.

Rising rates matter for two practical reasons. More infections in a community mean a higher chance of encountering one, including among people who have few partners. Infections in pregnancy are also rising, and untreated syphilis in pregnancy can cause serious harm to a baby, according to the CDC.

None of this is a reason for fear. It is a reason to treat syphilis testing as ordinary, routine health care.

Syphilis in Chicago and Illinois: the numbers

The Illinois Department of Public Health (IDPH) publishes county and city case counts. Here is what the most recent published figures show.

Measure	Rate per 100,000	Cases	Source
Chicago, primary and secondary syphilis (2022)	29.9	806	IDPH STI Section
Chicago, early syphilis (2022)	62.6	1,687	IDPH STI Section
Illinois, primary and secondary syphilis (2023)	11.6	1,457	CDC 2023 state ranking tables

These two rows come from different years and different publishers, so they should not be compared as if they were the same. IDPH also calculates its rates using 2010 Census population figures. Even so, the Chicago figure is a reminder that syphilis is a real local health issue, not a distant one.

The CDC's 2023 state tables also report 100 congenital syphilis cases in Illinois, a rate of 77.9 per 100,000 live births. That is why prenatal screening matters, and why Illinois law addresses it, as covered below.

For HIV, IDPH's December 2025 surveillance update lists 474 new diagnoses reported in the Chicago Health Department jurisdiction, and it labels those data provisional and subject to change. The count is likely to rise as reports come in, so it should not be read as a final annual total. It is mentioned here because the CDC recommends an HIV test for anyone diagnosed with syphilis.

How syphilis is tested

Most syphilis testing is done with a blood draw. The CDC STI Treatment Guidelines describe two kinds of blood tests, and the two are usually used together to confirm a result.

Non-treponemal tests

These tests (RPR and VDRL are common names) detect substances the body makes in response to damage from the infection. They give a result as a number called a titer. The titer is useful for tracking, because it generally falls after successful treatment. These tests can occasionally show a positive result for reasons other than syphilis, so a clinician usually confirms with the second type.

Treponemal tests

These tests detect antibodies aimed specifically at the syphilis bacterium. Names you may see include TP-PA, EIA, CIA and FTA-ABS. According to the CDC, treponemal tests usually stay positive for life, even after successful treatment. That does not mean the infection is still active. It is why a clinician uses a non-treponemal titer to follow treatment, not a treponemal test.

Some labs begin with the treponemal test and then run the other as confirmation. This is sometimes called the reverse sequence. Either order is described in CDC guidance, and results are always read together with symptoms and history by a clinician.

Other methods

If someone has an open sore, a clinician may also collect a sample from it for direct examination under a microscope or a lab test. That is not available at every site.

Timing and window periods

Very recent infection may not show up on a blood test yet. The CDC does not set one single number that fits every test and every person, and this page does not offer one. A clinician can tell you whether a retest makes sense after a recent exposure.

Who should be screened

The U.S. Preventive Services Task Force (USPSTF) recommends screening for people at increased risk for syphilis and for all pregnant people. The CDC advises that every pregnant person be screened at the first prenatal visit, with more screening in some situations. It also recommends at least yearly screening for sexually active men who have sex with men, with more frequent screening for some people.

The CDC also recommends that people with syphilis be tested for HIV, and that people who test positive for HIV be screened for syphilis, because the infections often occur together.

Syphilis treatment: what a clinician prescribes

For syphilis treatment, the CDC (2021) names penicillin as the preferred medicine for all stages. A clinician chooses the form, the length of treatment and the number of visits based on the stage. Early syphilis and later-stage syphilis are not handled the same way, and neurosyphilis, ocular syphilis and otosyphilis need their own evaluation.

Safety profile and special situations

Penicillin allergy. Tell the clinician about any past reaction. For people who are not pregnant, the CDC lists alternatives that a clinician can consider. In pregnancy, the CDC says penicillin is the only recommended treatment, so a person with a penicillin allergy is typically referred for allergy evaluation and desensitization. Do not skip or switch treatment on your own.
Pregnancy. Treatment during pregnancy is important for protecting the baby. The CDC recommends prompt treatment and careful follow-up.
HIV. People living with HIV can be treated for syphilis, and the CDC gives specific guidance on follow-up for them. A clinician will tailor the monitoring.
A short-lived reaction. Some people get fever, chills, headache or muscle aches within about a day after the first treatment. The CDC calls this the Jarisch-Herxheimer reaction. It is not an allergic reaction, and it usually passes within a day or so. Tell the clinic if symptoms are strong or last longer.

What happens after treatment

The CDC advises avoiding sexual contact until treatment is complete and any sores have fully healed. Recent partners may need testing and, in some cases, treatment even before their own results are in. The CDC guidance covers partners from the previous 90 days for early syphilis, and the clinic can walk through who that includes.

In Illinois, expedited partner therapy (EPT) is permitted for chlamydia, gonorrhea and trichomoniasis, according to the CDC's legal status page for the state. It does not cover syphilis, so partners of someone with syphilis need to be seen by a clinician.

Follow-up blood tests

Treatment is not the last step. The CDC recommends repeat non-treponemal blood tests after treatment to check that the titer is falling. For early syphilis, the guidelines call for follow-up testing at about 6 and 12 months. Other stages and people living with HIV may be checked on a different schedule, and a clinician sets the plan.

A falling titer suggests treatment worked. Some people have a titer that stays low but does not reach zero. This is called serofast, and it does not necessarily mean the infection is active. A clinician will decide whether any further evaluation is needed.

It is worth knowing that a person who has been treated will often stay positive on treponemal tests. This is expected. Keep a record of your treatment date, because it helps any clinician you see later read your results correctly.

Research findings, framed with care

Research on syphilis is active. A few observations are worth knowing, with the usual caution that research suggests and does not prove.

Doxycycline after sex. The CDC issued guidance in 2024 on doxycycline post-exposure prophylaxis (doxy-PEP). Studies reviewed by the CDC suggest it can lower the chance of syphilis, chlamydia and gonorrhea in some groups, including men who have sex with men and transgender women who have had a bacterial STI in the past year. It does not replace regular testing. Howard Brown Health offers doxy-PEP by appointment, and the Illinois Department of Public Health lists doxy-PEP guidance on its STD page.
Congenital syphilis. The CDC and USPSTF both link prenatal screening to better outcomes for babies. That is the evidence behind the testing schedule in Illinois law.
Syphilis and HIV. The CDC notes that a syphilis sore can make it easier to acquire or pass HIV. Treating syphilis and testing for both are routine parts of care.

What Illinois law says

A few Illinois rules are relevant to syphilis testing in Chicago.

Prenatal screening. Under the Illinois Prenatal Syphilis Act (410 ILCS 320/1), a syphilis test is required at the first prenatal exam and again in the third trimester, between 27 and 32 weeks of pregnancy. The law does not apply to a person who objects on religious grounds. Birth certificates record whether a test was done, the date and the lab, but never the result.
Consent for young people. Under the Consent by Minors to Health Care Services Act (410 ILCS 210/4), a minor aged 12 or older who may have come into contact with a sexually transmitted infection can consent to care related to prevention, diagnosis or treatment. Parental consent is not needed. Providers are directed to make reasonable efforts to involve family if they believe it will not be harmful.
Reporting. Syphilis is a reportable infection in Illinois. Under the Illinois Administrative Code (77 Ill. Adm. Code Part 693), health care professionals report within seven days of diagnosis or treatment, and in Chicago those reports go to the city health department. This is routine public health practice, and it is how partners can be reached and trends tracked.

Where to get tested in Chicago

Several Chicago options offer syphilis testing. Details below come from each organization's own page, and the sources are listed at the end. Hours and walk-in rules change, so call before you go.

Clinic	Address and phone	Cost and walk-in details
CDPH Sexual Health Specialty Clinic, Lakeview (North Clark Street Health Clinic)	2849 N. Clark St., 1st Fl.; 312.744.5507	The Chicago Department of Public Health says care is provided regardless of ability to pay or insurance status. Its page asks insured patients to bring an insurance card and does not say the visit is free. Call for an appointment; limited walk-ins. Closed 12 to 1 pm daily and on City holidays.
CDPH Sexual Health Specialty Clinic, Austin (West Division Street Health Hub)	4909 W. Division St., Suite 411; 312.746.4871	Same CDPH policy as above. Call for an appointment; limited walk-ins.
CDPH Sexual Health Specialty Clinic, Roseland (East 115th Street Health Hub)	200 E. 115th St., 1.5 fl.; 312.747.1090	Same CDPH policy as above. Call for an appointment; limited walk-ins.
Ruth M. Rothstein CORE Center (Cook County Health)	2020 W. Harrison St., 60612; 312-572-4700	Walk-in STI Screening Clinic. Cook County Health says to call Monday to Friday, 8:30 am to 3:30 pm, and that same-day HIV and STI services are provided. CDC GetTested lists a sliding scale and accepted insurance.
Howard Brown Health (Sheridan, 63rd St. and Broadway Youth Center locations)	4025 N. Sheridan Rd.; 641 W. 63rd St.; 1023 W. Irving Park Rd.; 773.388.1600	Walk-in sexual health clinic, no appointment needed, first come first served. Howard Brown describes it as low-cost and offers a sliding fee program based on income and family size. Its page lists syphilis testing and treatment. The Broadway Youth Center serves ages 12 to 24, per Howard Brown's site.
Planned Parenthood of Illinois, Rogers Park	5725 N Broadway; (773) 942-7193	CDC GetTested lists an appointment as required and insurance and Medicaid as accepted. It does not list a sliding scale. Confirm hours with the center.

For the full local list, see our Chicago clinic directory. For a broader guide to costs and what to expect at a visit, read STD testing in Chicago: where to get tested and what it costs.

The CDC also runs a national locator at gettested.cdc.gov, where you can look up testing sites by ZIP code. The Illinois HIV/STD Hotline at 1-800-243-2437 is another free starting point, according to IDPH.

The Chicago Department of Public Health does not publish a price for its clinic visits, so ask when you call. The same goes for the Planned Parenthood visit, where the listing does not say how much a self-pay patient would owe.

Quality indicators when choosing where to test

Since this is a health service and not a product, quality comes down to how a clinic works. These are reasonable things to look for.

A public health or licensed health center. Health department clinics, community health centers and hospital programs follow the CDC guidance and report results the way Illinois requires.
Clear counseling on what is being tested. Syphilis is not always included in a basic panel. It is fine to ask whether it is part of the visit, and to ask about chlamydia and gonorrhea too. For those, see our guide to chlamydia symptoms, testing and treatment in Chicago.
A plan for results and treatment. A good clinic tells you how you will hear back, and what happens if a result is positive, including treatment and follow-up.
Privacy and respect. You should be treated without judgment, whatever your gender, orientation or number of partners.

Questions to bring to a visit

Which tests are included, and does that include syphilis, HIV, chlamydia and gonorrhea?
Do I need to retest later, given when my last exposure was?
If treatment is needed, can it happen at this clinic?
When will I need follow-up blood tests?
How will my partners be notified, and can the clinic help?

Taking the next step

Syphilis can be quiet, but it can be found with a blood test and cured with treatment from a clinician. For a person in Chicago, that means one call or one walk-in visit. Free and low-cost options exist, and no one at a clinic needs a reason beyond wanting to know.

If you notice a sore, a rash or any of the symptoms above, or if a partner has told you they were diagnosed, contact a clinic soon.

Syphilis in Chicago: Symptoms, Testing and Treatment