Syphilis symptoms, window period and RPR testing in Taichung

In short

• Incubation period: 10 to 90 days, usually about 3 weeks. You may have no symptoms yet and still pass the infection on.
• The first symptom is a sore that does not hurt. It heals by itself even without treatment, and that is the step most often missed.
• The two blood tests turn positive at different times. Treponemal tests: about 5 to 15 days. Non-treponemal tests, such as RPR: about 6 weeks. Testing too early can give a false negative.
• Treatment is mainly long-acting penicillin, injected into muscle. One injection for early syphilis; one a week for three weeks for late syphilis. Afterwards the blood number falls slowly: a negative result is not the goal, and the response is judged by how far it falls.

How common is syphilis in Taiwan?

Syphilis has not gone away. Taiwan CDC recorded 9,738 notifications in 2024, and cases have risen since 2020. Syphilis is a category 3 notifiable communicable disease in Taiwan. We are required by law to report certain infections to the health authority. Your personal information is protected by the Communicable Disease Control Act, Article 10.

From exposure to the first symptoms

The incubation period is 10 to 90 days, usually about 3 weeks. Having no symptoms on day 5 does not mean you are not infected, and a sore on day 60 is still normal. Syphilis spreads most easily during sex and intimate contact, through direct contact with fluid from a lesion on the skin, the genital mucosa or the mouth. Oral sex also passes it on, and a lesion in the mouth or throat is usually not noticed.

Primary stage. A single ulcer that does not hurt or itch appears at the place of infection. It is called a chancre, and the clear fluid it releases when pressed is highly infectious. It often sits where you cannot see it: inside the foreskin, at the anus, in the mouth, in the vagina. It can also be multiple, unusual or painful, so an odd-looking sore does not exclude syphilis. Without treatment it heals after a few weeks. That is not recovery: the bacteria are by then spreading to the lymph nodes and the blood.

Secondary stage. About 25% of untreated people reach this stage, a few weeks to a few months after the ulcer. The commonest sign is a rash: usually symmetrical, not painful, and often on the palms and the soles, where most skin conditions do not appear. Fever, headache, poor appetite and swollen lymph nodes can also occur. The rash is easily mistaken for an allergy or a fungal infection, and then the blood test is not done. After a recent sexual risk, a rash on the palms or soles is a reason to ask for a syphilis test.

Latent syphilis. No symptoms, but a positive blood test. It is divided into early latent (within the past year), late latent (more than a year ago) and unknown duration, and that decides how long the treatment course is. So the doctor asks when you were last tested and when your last risky contact was; old health-check or blood donation reports make the staging more accurate.

Forms that can occur at any stage

Late syphilis can involve the heart and blood vessels, and can cause granulomatous lumps (gumma) and late damage to the spinal cord and brain. Three forms can occur at any stage, not only late: neurosyphilis in the nervous system (meningitis, stroke, a sudden change in mental state); ocular syphilis in the eye, which can cause permanent loss of vision; and otosyphilis in the ear (ringing, vertigo, sometimes sudden hearing loss).

When is a test accurate? Two blood tests, two window periods

Two terms are often mixed up. The incubation period is the time until symptoms appear; the window period is the time until a test can detect the infection. Almost all syphilis is diagnosed from a blood test, and the two groups of test have different window periods. Non-treponemal tests measure the body’s general reaction to the infection; treponemal tests look for antibodies against the bacterium itself, Treponema pallidum.

“It happened last week, so a test now will tell me.” Not necessarily. If only RPR is done, it can still be negative within six weeks of infection, and that negative proves nothing.

“I was treated. Why am I still positive?” Because a treponemal test cannot tell a current infection from a treated past one. About 15% to 25% do become negative within 2 to 3 years, but only among those treated very early.

So do not rely on one test after a recent contact. If the contact was high-risk and the first result is “treponemal test positive, RPR negative”, the guideline advises testing again 2 to 4 weeks later. Not sure what to test or when? See how to choose an STI test in Taichung (Chinese).

Reading the report: what 1:16 means

An RPR result is written as a titre: 1:2, 1:8, 1:16, 1:32. It shows how far the serum, the liquid part of the blood, can be diluted and still give a reaction; the larger the second number, the higher the activity.

• A response to treatment means the titre falls fourfold, two dilution steps: for example 1:16 to 1:4.
• A rising titre can mean reinfection or treatment failure, and needs reassessment. In some people (serofast) it falls but never becomes negative, with no sign of reinfection.
• Results from different laboratories are hard to compare, so stay with one for follow-up.

RPR can also be positive when there is no syphilis; known associated factors include HIV infection, autoimmune disease, vaccination, injecting drugs, pregnancy and older age. So one positive RPR is not a diagnosis: it needs a treponemal test and clinical assessment beside it. A positive treponemal test also does not mean you are infected now.

Treatment, and a reaction that can occur on the day

Under the 2025 Taiwan guideline on syphilis and gonorrhoea in adults (Taiwan CDC and the Infectious Diseases Society of Taiwan), the main treatment is long-acting penicillin (benzathine penicillin G) by deep injection into muscle.

The injection can only be given deep into muscle, usually the buttock, never into a vein. It must be kept refrigerated and not every clinic holds stock, so check first. For people with HIV infection, treatment is currently the same as for people without HIV. In pregnancy it is also the main treatment; if the woman is allergic to penicillin, the guideline advises desensitisation and then using penicillin.

About 90% of people who report a penicillin allergy are found not to be allergic. For people who are not pregnant, the alternatives are oral doxycycline (a longer course in late than in early syphilis) or ceftriaxone injections; these carry a weaker recommendation and need a doctor’s assessment.

The Jarisch–Herxheimer reaction. It happens when large numbers of the bacteria are killed and the substances released over-stimulate the immune system. It can cause sudden fever, chills, muscle pain, a fast heartbeat, flushing, a worsening rash or mildly low blood pressure, usually within 4 to 6 hours of treatment and lasting 12 to 24 hours. It is not a drug allergy and not a sign of worsening disease, and cannot be prevented. The doctor explains it beforehand and provides medicine for fever and pain.

If you are allergic to penicillin. An allergic reaction to penicillin is reported in about 1% to 10% of people; as noted above, about 90% of those reports turn out on assessment not to be a true penicillin allergy. Most reactions are hives or itchy skin. Severe anaphylactic shock occurs in about 0.015% to 0.04%.

If the symptoms of the Jarisch–Herxheimer reaction are severe, or last longer than a day, come back to be assessed.

Is it over once treatment is finished?

No. The day treatment ends is the day follow-up begins.

• The RPR titre has to be followed. Success means a fourfold fall, not a negative test; a rising number can mean reinfection or treatment failure, and the two are handled differently. The doctor sets the schedule by stage.
• Partners need testing too. Reinfection between partners is common; treating only one person often means it returns months later.
• Being cured does not make you immune. Having had syphilis gives no protection; you can be infected again.

Most early syphilis can be cured with adequate treatment, though that depends on the stage, the response and the follow-up. The guideline also states that everyone with early syphilis should be tested for HIV at diagnosis and treatment, that those who are HIV-negative and in a high-risk group should be given advice on pre-exposure prophylaxis (PrEP), and that the HIV test should be repeated 3 months later. The behaviour that leads to syphilis also exposes a person to HIV, and syphilis lesions raise that risk further. See HIV RT-PCR ultra-early detection (Chinese).

Prevention: condoms, and where Doxy-PEP fits

Correct use of a condom throughout sex remains the base. Beyond that, the Taiwan guideline adds one option: Doxy-PEP, a single oral dose of doxycycline after exposure. PEP means post-exposure prophylaxis: medicine taken after a risk to prevent an infection.

• For men who have sex with men, and transgender women, at risk of syphilis and chlamydia, it should be offered through shared decision-making, within 24 hours and no later than 72 hours after risky sex. (Recommendation: strong; evidence: high.)
• For cisgender women and heterosexual men, there is at present no such recommendation.
• For preventing gonorrhoea it is not recommended. Taiwan CDC monitoring in 2024 showed close to 80% of gonococcal strains in Taiwan already resistant to tetracycline-class antibiotics.

That rests on resistance inside Taiwan, which differs a great deal between regions, so an exposure abroad is assessed differently. Doxy-PEP does not prevent viral infections and does not replace screening.

Getting checked in Taichung

• Symptoms, or a clear exposure: book a consultation. A description cannot replace an examination of the lesion.
• You would rather not have a record: several anonymous routes exist in Taichung, listed in anonymous screening in Taichung (Chinese).
• A positive result from elsewhere: bring the report, so the stage can be set and follow-up arranged.

Three things usually decide what to test: how long ago the exposure was, what kind of sex, and whether you have symptoms. Please bring your passport or resident certificate; it is needed to create the medical record. If you are not enrolled in Taiwan’s National Health Insurance, the consultation and tests are self-paid. Costs are explained at the consultation.

This clinic is a Taiwan CDC anonymous screening facility (institution code 3503241524). For this service we do not check your National Health Insurance card or any identity document, so it is open to you regardless of nationality. There is no charge for it. No formal report can be issued, because no identifying information is recorded. The anonymous service covers HIV, by rapid blood test.

Taiwan CDC separately provides free rapid syphilis screening for people aged 24 or under and for students; kit numbers are limited, so confirm sessions first.

Related pages

• STI screening: what and when (Chinese)
• After a possible exposure: when to test (Chinese)
• Anonymous screening in Taichung (Chinese)
• HIV RT-PCR: shortening the window period (Chinese)

Appointments and access

Consultations are conducted in Mandarin, and can also be conducted in English.

昭安泌尿科診所 (Morning Urology Clinic)
No. 98, Boguan 2nd St., West District, Taichung City 403, Taiwan（403 臺中市西區博館二街98號）
Consulting hours: Monday to Saturday (closed Sunday). Online booking is open 24 hours.

This page was produced by 昭安泌尿科診所 (Morning Urology Clinic). Medical content last updated: August 2026 (same as the Traditional Chinese version). English version published: 4 September 2026. Medically reviewed by Dr. Chao-An Chen, urologist.

Sources: Taiwan CDC and the Infectious Diseases Society of Taiwan, Taiwan guideline on syphilis and gonorrhoea in adults, 1st edition, 2025 / Taiwan CDC, syphilis disease information and notification statistics / Ghanem KG, et al. N Engl J Med. 2020;382(9):845-854 / Workowski KA, et al. MMWR Recomm Rep. 2021;70(4):1-187. Figures are 2024 notification data; the latest Taiwan CDC statistics take precedence.

This page provides general medical information and does not replace an individual diagnosis or treatment plan. The stage, the course length and the follow-up schedule are decided by a doctor after assessing your history, symptoms and results.