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 spreads through sexual contact. It is also one of the most treatable infections in this part of medicine. A clinician can test for it with a blood draw, and the CDC says it can be cured with the right antibiotic.

The hard part is that syphilis is easy to miss. The first sign can be a small sore that does not hurt. Later signs can look like many other things. Many people have no symptoms for long stretches.

This guide walks through what is known about the organism, the stages, the blood tests, treatment, and follow-up. It also covers what Houston and Texas health agencies report and where to get tested in the city.

What causes syphilis: the organism

Syphilis is caused by a spiral-shaped bacterium called Treponema pallidum. Under a microscope it looks like a thin corkscrew. That shape helps it move through body tissue, which is one reason it can spread from the first site of infection to the blood and other organs.

Research on this bacterium has been hard because it has been difficult to grow in a lab. Scientists have described it as having a very thin outer membrane with few surface proteins. Research suggests this may help it avoid some immune responses, which could explain why the infection can persist for years without treatment. These are laboratory observations. They do not change what a clinician does for a patient.

The same biology shapes testing. The immune system makes two broad kinds of antibodies in response to the infection. Those two groups are what the blood tests look for. They are explained below.

Syphilis spreads through direct contact with a syphilis sore, usually during vaginal, anal or oral sex, according to the CDC. It can also pass from a pregnant person to a baby. It does not spread through toilet seats, doorknobs or shared dishes.

The stages and syphilis symptoms

The CDC STI Treatment Guidelines (2021) describe syphilis in stages. Not everyone moves through each stage in a neat order, and stages can overlap.

Primary stage

The CDC says the time from exposure to the first sign ranges from 10 to 90 days, with an average of about 3 weeks. The first sign is usually a single firm, round sore called a chancre. It is typically painless.

Because it does not hurt, it can go unnoticed. It can also appear where no one is looking, such as inside the vagina, in the rectum or in the mouth. The sore heals on its own in a few weeks. Healing does not mean the infection is gone.

Secondary stage: the syphilis rash

The CDC describes the secondary stage as beginning weeks to months after the first sore. The best known sign is a syphilis rash. It is often described as rough, reddish or reddish-brown spots. It can show up on the chest, back, arms and legs. It often appears on the palms of the hands and the soles of the feet.

The rash usually does not itch, and it can be faint. It can also look like rashes from other causes, such as allergies, medicines or viral illnesses. That is why a rash alone cannot say what is behind it. A clinician looks at the whole picture and orders a blood test.

Other secondary signs listed by the CDC include:

Fever and tiredness
Sore throat
Swollen glands
Patchy hair loss
Headaches and muscle aches
Flat, wart-like patches in warm, moist areas
Mouth sores

These signs also fade without treatment. A person can feel well again while the infection continues.

Latent stage

In the latent stage there are no signs or symptoms. The infection is still present and can only be found through a blood test. The CDC separates early latent syphilis from late latent syphilis based on how long ago the infection was likely acquired, because that guides treatment.

Tertiary stage and other complications

Without treatment, the CDC says some people go on to develop tertiary syphilis years or decades later. It can affect the heart, blood vessels, brain and nerves. This is uncommon where treatment is available, and it is a main reason clinicians encourage testing.

Syphilis can also reach the nervous system, the eyes or the ears at any stage. The CDC calls these neurosyphilis, ocular syphilis and otic syphilis. Vision changes, hearing changes, severe headache or confusion are reasons to seek care promptly. A clinician can sort out the cause.

Why the national rise matters

The CDC reports that syphilis rates in the United States have risen in recent years after reaching a historic low around the year 2000. The increase has been seen among men and women, across racial and ethnic groups, and across regions.

The rise in congenital syphilis, which is syphilis passed to a baby during pregnancy, has drawn particular concern. CDC surveillance for 2023 lists 930 congenital syphilis cases in Texas, a rate of 238.6 per 100,000 live births. Congenital syphilis can cause serious harm to a baby, but it is largely preventable when a pregnant person is tested and treated in time.

Research suggests several reasons for the increase, including gaps in testing, gaps in access to care and shifting patterns of sexual networks. For a reader, the practical point is simple. Syphilis is common enough that routine testing is a normal part of sexual health care.

The USPSTF recommends syphilis screening for people at increased risk, and for all pregnant people. The CDC adds that sexually active people may talk with a clinician about how often screening makes sense for them. The CDC's 2024 doxy-PEP guidance also notes that clinicians may discuss doxycycline after sex for some people, and that regular syphilis testing remains part of that care. Whether this applies to a given person is a conversation for a clinician.

Syphilis in Houston and Texas: what the data show

The most recent county-level figures in the Texas Department of State Health Services (DSHS) Texas STD Surveillance Report cover 2022. They are counts of reported cases, so they reflect both infections and how much testing is done.

Measure (2022, Texas DSHS)	Harris County	Texas
Primary and secondary syphilis cases	1,082	4,655 (15.5 per 100,000)
All stages of syphilis, total cases	5,670	25,991 (86.6 per 100,000)

The DSHS report does not publish a county rate for syphilis in Harris County, so no county rate is shown here. Using the same DSHS source, Harris County accounts for about 23 percent of the state's primary and secondary cases and about 22 percent of all reported syphilis cases in Texas.

These are older figures. DSHS notes that prior-year numbers can change, and newer numbers may differ. Check the DSHS HIV/STD reports page for the latest release.

Texas law also shapes how syphilis is tracked. The DSHS Texas Notifiable Conditions list for 2026 includes syphilis in all stages. Providers report primary and secondary syphilis within 1 work day and other stages, including congenital syphilis, within 1 week. Reporting goes to public health so that staff can offer help with partner notification and follow-up.

Blood tests for syphilis: treponemal and non-treponemal

The CDC STI Treatment Guidelines (2021) explain that most syphilis diagnosis relies on two kinds of blood tests used together. Each answers a different question.

Treponemal tests

These tests look for antibodies made against the syphilis bacterium itself. They are sensitive and specific. A treponemal test usually stays reactive for life, even after successful treatment. That is expected, and it does not mean treatment failed.

Non-treponemal tests

These tests, such as RPR and VDRL, measure antibodies to substances released from damaged cells. Results come back as a number called a titer, like 1:8 or 1:32. The titer matters because it can be tracked over time. After effective treatment, the titer generally falls. It may become very low or non-reactive.

Why two tests

Using both tests lowers the chance of a misleading result. Some other conditions can cause a false-positive non-treponemal result, and a second test helps sort that out. Labs use either the traditional order (non-treponemal first, then treponemal) or the reverse order (treponemal first). The CDC describes both as acceptable. A clinician will explain which approach their lab uses.

Two other points from the CDC are worth knowing:

If a sore is present, a clinician may take a swab from it for direct testing in some settings.
Very early in an infection, blood tests can still be negative. A clinician can say whether a repeat test makes sense. Ask the clinic about the timing that applies to the situation, and rely on the CDC guidance they follow rather than a number found elsewhere.

Syphilis testing is not part of every standard STI panel. A person who wants a syphilis test can ask for it by name.

Is syphilis curable?

Yes. The CDC says syphilis can be cured with antibiotics prescribed by a clinician. Penicillin is the preferred treatment at every stage, and it is the only recommended option during pregnancy.

The details of treatment are decided by a clinician. The type of penicillin, how it is given and how long treatment lasts depend on the stage and on whether the nervous system, eyes or ears are involved. Treatment for syphilis is not something to start on one's own, and leftover antibiotics are not a substitute.

Safety profile and things to tell a clinician

Penicillin has been used for syphilis for many decades and has a long safety record. A few points are worth raising at a visit:

Penicillin allergy. Tell the clinician about any past reaction. The CDC notes that many people who report an allergy are not truly allergic, and testing can sometimes clarify this. For people who are allergic, a clinician may use another antibiotic, or in pregnancy may arrange a special process to allow penicillin.
The Jarisch-Herxheimer reaction. The CDC describes a short-lived reaction in the first day after treatment that can include fever, chills, headache and muscle aches. It is caused by the body's response to the bacteria dying off. Clinicians can advise on what to expect.
Pregnancy. Treatment during pregnancy protects the baby when it is given in time, according to the CDC.
HIV. People with HIV can be treated for syphilis, and clinicians may follow up more closely.

One caution from the CDC is that treatment stops the infection, but it cannot undo damage that already happened. This is another reason earlier testing helps. Another is that a person can get syphilis again after being cured. Having had it does not protect against future infection.

Follow-up blood tests after treatment

After treatment, a clinician will usually ask for repeat blood tests. This follow-up is how a clinician checks that the infection responded.

The CDC STI Treatment Guidelines (2021) describe repeating non-treponemal titers at set intervals. For early syphilis, that generally means checks around 6 and 12 months after treatment. The CDC looks for a fourfold drop in the titer, which is a change of two dilutions, such as from 1:32 to 1:8. Schedules can differ for later stages, for pregnancy and for people with HIV, so a clinician's plan is the one to follow.

Some people have a titer that stays low but does not fall to zero. The CDC calls this a serofast state. It is not always a sign of treatment failure, and a clinician decides whether anything more is needed.

Partners, pregnancy, teens and privacy in Texas

Partners. The CDC advises that recent partners be tested and may be treated. Texas has no EPT statute, but CDC's Legal Status of EPT in Texas page says Texas Medical Board rules allow physicians to prescribe for partners of an established patient. Pharmacists may dispense those prescriptions. A clinic or the health department can explain how this works and can help notify partners without naming the patient.

Pregnancy. Under Texas Health and Safety Code Sec. 81.090, a syphilis test is required at the first prenatal visit and again in the third trimester, not earlier than the 28th week. A syphilis test is also done at delivery. Unlike the HIV tests in that law, the syphilis tests are not optional for the patient to decline.

Teens. Texas Family Code Sec. 32.003 lets a minor of any age consent to diagnosis and treatment of a reportable infectious disease, which covers syphilis. Parent consent is not needed. The statute does allow a physician to tell a parent or guardian, so a teen who is worried about privacy should ask the clinic how it handles that before the visit. Houston Health Department also notes that a Texas law that took effect September 1, 2025 gives parents access to a minor's electronic health record, which is another reason to ask.

Where to get a syphilis test in Houston

Several Houston clinics test for syphilis at no cost or on a sliding scale. The full list, with details on costs and services, is in our guide to STD testing in Houston. A summary of clinics that list syphilis testing:

Clinic	Address and phone	What the source says
Houston Health Department: Northside Health Center	8504 Schuller Rd., Houston, TX 77093; 832-393-4220	STD walk-in services; sliding scale
Houston Health Department: Sharpstown Health Services	6201 Bonhomme Rd., 3rd Floor, South Tower, Houston, TX 77036; 832-393-4220	STD walk-in services; sliding scale
Houston Health Department: Sunnyside Health and Multi-Service Center	4410 Reed Rd., Houston, TX 77051; 832-393-4220	STD walk-in services; sliding scale
Harris County Public Health Antoine Clinic	5815 Antoine Dr, Houston, TX 77091; 832-927-7350	Free; walk-ins welcome; Monday to Thursday 8am to 7pm, Friday closed, every other Saturday 8am to 2pm
Legacy Community Health, Montrose	1415 California St., Houston, TX 77006; (832) 548-5100	Syphilis testing free; walk-in HIV, syphilis and hepatitis C testing
Avenue 360 Health and Wellness (Heights and Midtown)	2150 West 18th Street, Suite 300, Houston, TX 77008, and 2920 Fannin St., Houston, TX 77002; (713) 426-0027	Free walk-in rapid syphilis testing, Monday to Friday 8:30am to 4:30pm
The Montrose Center	401 Branard Street, Houston, TX 77006; 713-529-0037	Free walk-in rapid syphilis testing, Monday to Thursday 9am to 2pm

Houston Health Department says its sexual health clinics are encouraging appointments as of September 1, 2026. Walk-ins are still seen as capacity permits, but a visit is not guaranteed. Calling first is a good idea. Hours and services can change, so confirm with the clinic before going.

Other options:

Test for Texas. DSHS lists a free mail-order self-collection kit that includes syphilis, HIV, gonorrhea and chlamydia for anyone in Texas aged 13 and older. No insurance is needed. Orders go through testfortexas.org.
Testing123. Harris County Public Health says its mobile team offers free HIV and syphilis testing at a location you choose in Harris or Montgomery County. Text (281) 962-8378.
CDC GetTested. The CDC's gettested.cdc.gov locator lists more testing sites by ZIP code.

Quality indicators when choosing where to test

This section covers how to judge a testing source, which is a useful way to think about sourcing. Some things to look for:

A named operator. Health departments, community health centers and established nonprofits publish who runs the clinic and what it offers.
Clear test descriptions. A good source states whether it offers a full panel or only rapid syphilis testing. For example, The Montrose Center and Avenue 360 list rapid syphilis testing and not a full STI panel.
Follow-up care. Ask what happens if a result is reactive. Clinics that can treat on site or refer you quickly make the next step easier.
Plain pricing. If a page does not list a price, call and ask. Legacy's page, for instance, does not list pricing for its full STI panel.
Privacy information. Ask how results are shared and how reporting works.

It also helps to ask which tests are included, since a syphilis test might not be part of the default panel.

A calm way to think about next steps

Syphilis is common enough to be part of routine sexual health care and treatable enough that finding it is good news compared with missing it. Anyone who is sexually active, whatever their gender or orientation, can ask a clinician about testing. People with a new sore, an unexplained rash, a new partner or a pregnancy have a clear reason to ask.

A clinician can explain what a result means, what treatment would involve and what follow-up to expect. That conversation is the part no article can replace.

Syphilis in Houston: Symptoms, Testing and Treatment