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 has been rising across the United States, and Texas is part of that trend. The good news is that it is well understood. A blood test can find it, and a clinician can treat it.

This guide covers the organism behind syphilis, the stages, the rash, how the blood tests work, what treatment looks like, and where to get tested in San Antonio. It is written for every reader, whatever your gender, orientation or relationship status. Syphilis can affect anyone who is sexually active, and it can pass from a pregnant person to a baby.

The organism: what causes syphilis

Syphilis is caused by a bacterium called Treponema pallidum, subspecies pallidum. Under a microscope it is a thin, tightly coiled spiral, which is why it belongs to a group of bacteria called spirochetes.

A few features of its biology explain how syphilis behaves in real life.

It is fragile outside the body. The bacterium does not survive long on surfaces. The CDC says it spreads through direct contact with a syphilis sore or rash during vaginal, anal or oral sex.
It has a thin outer membrane with few surface proteins. Research suggests this helps it avoid some immune responses, which may be part of why untreated infection can stay in the body for years.
It cannot be grown easily in a lab dish. This is one reason diagnosis relies on blood tests that look for the body's response, rather than on culture.
It is sensitive to penicillin. The CDC STI Treatment Guidelines (2021) say penicillin is the preferred treatment at every stage.

The biology is the same wherever you live. What changes locally is how common syphilis is and where you can get tested.

The stages of syphilis

The CDC describes syphilis in stages. The stages can overlap, and many people do not notice the early ones. That is why testing matters more than watching for signs.

Primary stage

The CDC says the first sign is usually a sore called a chancre. It is typically firm, round and painless, so it is easy to miss. It can appear inside the vagina, rectum or mouth, where a person may not see it.

The CDC says the sore usually appears about 3 weeks after exposure, with a range of 10 to 90 days. Without treatment it heals on its own within a few weeks. Healing does not mean the infection has gone.

Secondary stage: the syphilis rash

The syphilis rash is the sign most people have heard of. The CDC says the secondary stage can bring a rash that may appear as the chancre is healing or several weeks afterward.

The CDC and the 2021 guidelines describe the rash and other secondary symptoms this way:

The rash is often rough, red or reddish-brown spots. It can show up on the palms and the soles of the feet, but it can also appear on the trunk or elsewhere.
It usually does not itch, though that is not a rule.
It can be faint enough to overlook, or look like other skin conditions.
Other symptoms can include fever, sore throat, swollen lymph nodes, patchy hair loss, headaches, tiredness and muscle aches.
Moist, wart-like patches can appear in warm areas such as the groin, and patches can appear in the mouth.

Many conditions cause rashes, so a rash alone cannot say whether syphilis is the cause. A clinician can examine the skin and order a blood test.

Latent stage

After the secondary stage, the CDC says syphilis can enter a latent stage with no visible signs. A person may feel completely well. A blood test is the only way to find it at this point. Early latent means the infection was acquired within the past year. Late latent, or unknown duration, covers the rest.

Tertiary stage

Without treatment, some people go on to tertiary syphilis. The CDC says this can appear 10 to 30 years after infection and can affect the heart, blood vessels, brain and nervous system. It is uncommon today, largely because syphilis can be found and treated earlier.

Nervous system, eye and ear involvement

The CDC STI Treatment Guidelines note that syphilis can affect the nervous system, the eyes or the ears at any stage. Symptoms can include severe headache, vision changes, hearing changes or dizziness. Anyone with these symptoms and a possible exposure should be seen promptly by a clinician.

Stage	What the CDC describes	How it is found
Primary	A usually painless sore (chancre), about 3 weeks after exposure on average	Exam and blood tests
Secondary	Rash, possibly on palms and soles, plus flu-like symptoms	Exam and blood tests
Latent	No signs or symptoms	Blood tests only
Tertiary	Organ damage, years to decades later	Clinical evaluation and blood tests

Why the national rise matters

The CDC has reported sharp increases in syphilis across the country in recent years. That includes congenital syphilis, which is syphilis passed from a pregnant person to a baby during pregnancy or birth.

Texas carries a large share of that burden. According to the CDC's 2023 STI surveillance state ranking tables, Texas reported 930 cases of congenital syphilis in 2023, a rate of 238.6 per 100,000 live births.

Why does this matter to an adult who is not pregnant? More cases in a community means a higher chance that any new partner has syphilis without knowing it. Early syphilis can be silent, so routine testing is one of the few dependable ways to find it.

The USPSTF recommends syphilis screening for adolescents and adults at increased risk, and for all pregnant people. A clinician can help you decide what makes sense for you.

Syphilis in San Antonio and Texas: the data

The most recent county figures published by the Texas Department of State Health Services (DSHS) come from its 2022 STD Surveillance Report. DSHS notes that prior-year numbers can shift slightly as data are cleaned.

Measure (2022, DSHS)	Bexar County	Texas
Primary and secondary syphilis cases	500	4,655
Primary and secondary rate per 100,000	24.3	15.5
Syphilis cases, all stages	2,602	25,991

Primary and secondary syphilis are the early stages. Bexar County's rate of 24.3 per 100,000 was higher than the statewide rate of 15.5 in the same year, according to DSHS. DSHS does not print a Bexar County rate for all stages combined, so only the case count is shown.

These numbers describe a community, not any one person. They are a reason for routine testing, not for alarm.

Research findings on how syphilis is detected

No single test does everything. The CDC STI Treatment Guidelines (2021) describe an approach that uses two different kinds of blood test. Research suggests that pairing them reduces the chance of a misleading result from either one alone.

Non-treponemal tests

These tests, often called RPR or VDRL, detect antibodies the body makes in response to the infection. They report a number called a titer, such as 1:8 or 1:32.

The titer is useful for tracking. A clinician compares it over time to see how the body is responding to treatment.
These tests can sometimes be reactive for reasons other than syphilis, which is called a false positive. That is why a second kind of test is used to confirm.

Treponemal tests

These tests, such as TP-PA, EIA/CIA or FTA-ABS, detect antibodies aimed at the syphilis bacterium itself.

The CDC says they generally stay reactive for life, even after successful treatment. A reactive treponemal test alone cannot show whether an infection is new, old or already treated.
Because of this, they are not used to track treatment response.

Putting the two together

Labs use one of two orders. In the traditional order, a non-treponemal test comes first and a treponemal test confirms it. In the reverse order, a treponemal screen comes first, followed by a non-treponemal test. When the two disagree, labs usually run a second treponemal test to sort it out.

You do not need to choose. What matters is knowing that one reactive result is not the whole story. A clinician reads the pattern along with your history and any exam findings.

Rapid tests

Some San Antonio sites offer a rapid fingerstick syphilis test, which gives a result during the visit. A reactive rapid result usually still needs follow-up blood work to confirm, so ask the clinic what happens next.

Timing

Antibodies take time to develop, so a test very soon after an exposure can be non-reactive even if an infection is present. The CDC gives the typical time to a first sore as about 3 weeks, with a range of 10 to 90 days. The CDC does not give a single cutoff after which one test is conclusive. If you tested soon after an exposure, ask the clinician whether and when to repeat it.

Is syphilis curable?

Yes. The CDC says syphilis is curable with the right antibiotic treatment from a clinician. This is true at every stage, though the approach differs depending on how long the infection has been present.

Here is what the CDC STI Treatment Guidelines (2021) describe:

Penicillin is the preferred syphilis treatment. A clinician decides the form and the length of treatment based on the stage and on whether the nervous system, eyes or ears are involved.
Treatment stops the infection from progressing. It does not reverse damage that has already happened, which is another reason earlier detection helps.
Other antibiotics are options in some non-pregnant people who cannot take penicillin. A clinician chooses these case by case.
Pregnancy is different. The guidelines say penicillin is the only recommended treatment during pregnancy. A pregnant person with a penicillin allergy is typically referred for allergy evaluation and desensitization so penicillin can still be used.

This page does not give doses or schedules. Those depend on the stage and on your own health, and they are for the prescribing clinician to set.

Safety profile and cautions

Penicillin has been used for syphilis for many decades. The CDC and the broader literature describe a few points worth knowing before a visit:

Allergy. Tell the clinician about any past reaction to penicillin or related antibiotics. Many people who think they are allergic turn out not to be when evaluated, and research suggests this evaluation can open up first-line treatment.
The Jarisch-Herxheimer reaction. The CDC says some people develop fever, chills, headache and muscle aches within the first day after treatment. It is a reaction to the bacteria being cleared, not an allergy, and it usually passes within a day. People who are pregnant should ask their clinician about it, since it can sometimes affect the pregnancy.
Medical history. Share any other medical conditions and medicines, including any history of HIV, since this can change how a clinician follows the infection.

Follow-up blood tests after treatment

Treatment is not the end of the process. The CDC STI Treatment Guidelines (2021) call for follow-up blood tests to confirm that the infection is responding.

A clinician repeats a non-treponemal test (the RPR or VDRL) and compares the titer with the one from before treatment.
For early syphilis, the guidelines recommend clinical and blood test follow-up at 6 and 12 months. Later-stage and special situations have their own schedules, which the clinician sets.
The goal is a clear drop in the titer. In many people it falls to a low level or becomes non-reactive over time. In some people it stays at a low, stable level for life, which is called serofast. A clinician can explain what your own numbers mean.
Treponemal tests usually stay reactive after treatment, so a reactive result years later does not by itself mean a new infection.

Keep your follow-up appointments even if you feel completely well. Syphilis is often silent, so feeling fine cannot confirm that treatment worked.

Partners and prevention

After a syphilis diagnosis, a clinician or the health department will talk with you about telling recent partners so they can be tested. The CDC describes partner notification as a standard part of care, and it can often be done without sharing your name.

In Texas, the CDC's legal summary notes that rules from the Texas Medical Board and the Texas pharmacy rules allow expedited partner therapy, where a clinician can prescribe STD medicine for the partner of an established patient. Ask your clinician whether it applies in your situation.

For people who are sexually active, the CDC lists condoms, regular testing and open conversations with partners as ways to lower risk. In 2024 the CDC also issued guidance on doxycycline taken after sex (doxy-PEP) for some gay, bisexual and other men who have sex with men, and for transgender women, who have had a bacterial STI in the past year. It is prescribed by a clinician. Whether it fits you is a conversation for a clinician.

Texas rules that apply to syphilis

Reporting. The Texas DSHS Notifiable Conditions list (2026) includes syphilis. Primary and secondary syphilis are reportable within 1 work day, and other stages, including congenital syphilis, within 1 week. Clinics and labs file these reports with the health department. This is a public-health process.
Pregnancy screening. Texas Health and Safety Code Sec. 81.090 calls for a syphilis test at the first prenatal visit, another in the third trimester (not earlier than the 28th week), and a test at delivery. A pregnant person may object to the HIV tests under that law, but not to the syphilis tests.
Teens. Under Texas Family Code Sec. 32.003, a minor of any age may consent to diagnosis and treatment of a reportable infectious disease, which covers syphilis. Parent consent is not needed. The same law allows a physician to tell a parent or guardian about the treatment, so a clinic cannot promise that parents will never be told.

Where to get tested for syphilis in San Antonio

Several San Antonio organizations test for syphilis. Details below come from each organization's own published information, and hours and services can change. Call before you go. For a longer list with more detail, see our guide to STD testing in San Antonio.

Where	What it publishes
Metro Health STI Walk-In Clinic 512 E. Highland, Suite 150, San Antonio, TX 78210 210-207-8830	STI and HIV testing, treatment and counseling. Walk-in. A $15 office visit administrative fee applies, and other fees vary by service. Hours: Monday to Thursday 7:45 a.m. to 4:30 p.m. (latest check-in 3 p.m.), Friday 7:45 a.m. to 12 p.m. (latest check-in 10:30 a.m.). Check-in may close early at capacity. The clinic serves San Antonio and Bexar County residents and those with no other way to get STI services. A photo ID is required and testing is not anonymous.
San Antonio AIDS Foundation (SAAF) 818 E. Grayson Street, San Antonio, TX 78208 (210) 225-4715	Rapid HIV, syphilis, gonorrhea and chlamydia testing. Screening and confirmatory services are listed as free, with no appointment needed. SAAF says gonorrhea and chlamydia results take 7 to 10 days. Hours: Monday, Wednesday and Thursday 8:30 to 4:00, Tuesday 12:00 to 8:00, Friday 9:00 to 1:00, Saturday 11:00 to 3:00, closed Sunday.
Alamo Area Resource Center (AARC) 303 N. Frio, San Antonio, TX 78207 (210) 625-7200	Free testing for HIV, hepatitis C, syphilis, gonorrhea and chlamydia, including rapid fingerstick tests for HIV, syphilis and hepatitis C. Walk-ins Monday to Friday 8 a.m. to 4:30 p.m., and Wednesday until 8 p.m.
Kind Clinic, San Antonio 730 Isom Road, San Antonio, TX 78216 833-937-5463 (general support line)	Walk-in HIV and STI testing and STI treatment. Its locations page lists clinic hours (Monday, Tuesday and Friday 9 a.m. to 5 p.m.; Wednesday and Thursday 9 a.m. to 8 p.m.; 2nd and 4th Saturdays 9 a.m. to 2 p.m.) and says walk-in testing hours differ, so call to confirm.
CommuniCare Apollo Wellness Clinic 6511 W Loop 1604 N, Ste. 105, San Antonio, TX 78254 (726) 224-3438	STD and HIV screening and testing, Monday to Friday 8 a.m. to 5 p.m. CommuniCare lists a sliding fee discount for self-pay patients with family income under 200% of federal poverty guidelines. Ask whether walk-ins are accepted.
BEAT AIDS 210.212.2266	Free, confidential HIV testing and testing and treatment for common STIs. The organization lists several San Antonio locations without saying which one does testing, so call first.
CentroMed 210-922-7000	Screening and treatment for sexually transmitted diseases, with a sliding fee scale based on income and family size. CentroMed has multiple clinics, so call to ask which location to visit.

The Metro Health sexual health page is at sa.gov. If a clinic's page does not list a price for a service, ask the clinic directly before your visit.

Testing at home

Texas DSHS runs Test for Texas, which mails free at-home kits for HIV, syphilis, gonorrhea and chlamydia to anyone in Texas aged 13 or older. Insurance is not needed. DSHS says results arrive in a secure portal seven business days after the sample reaches the lab. Orders are placed at testfortexas.org.

Quality indicators: what a good testing visit looks like

You may not be able to judge a lab, but you can judge a visit. These are signs of a well-run testing service:

It is run by a health department, a licensed clinic or a recognized community health organization.
Staff explain which infections the visit includes. Syphilis is not always part of a basic panel, so ask for it by name if you want it.
A reactive result leads to a clear next step, such as a confirmatory test or a treatment visit.
They tell you how and when results arrive.
They explain how your information is handled, including reporting to the health department.

You can also use the CDC's locator at gettested.cdc.gov to find testing sites by ZIP code.

What to do next

If you are sexually active and have not tested for syphilis, or you have had a new partner, a rash you cannot explain or a sore that came and went, a test can give you real information. Free and low-cost options exist in San Antonio, and a clinician can treat syphilis if it is found.

Pick the option that fits your schedule, call ahead to confirm hours, and bring a photo ID if you go to Metro Health. If you are pregnant or could become pregnant, tell the clinician so they can plan the right timing of tests.

Syphilis in San Antonio: Symptoms, Testing and Treatment