After exposure, the timing of symptoms depends on the organism. Chlamydia tends to show up within one to three weeks, syphilis sores around three weeks, trichomoniasis anywhere from five to twenty-eight days, and HIV's flu-like phase at two to four weeks. Herpes and gonorrhea timing isn't pinned to a fixed CDC window, and many infections cause no symptoms at all.
discharge and burning; can also hit throat/rectum
painful blisters that crust over; tends to recur
often silent; discharge or burning if anything
frothy, itchy discharge with an odor
| Item | Value |
|---|---|
| Gonorrhea | curable — discharge and burning; can also hit throat/rectum |
| Genital herpes | managed — painful blisters that crust over; tends to recur |
| Chlamydia | curable — often silent; discharge or burning if anything |
| Trichomoniasis | curable — frothy, itchy discharge with an odor |
The short list of likely causes
If you've got burning, discharge, sores, a rash, or flu-like illness in the days or weeks after sex, a handful of infections account for most of it: gonorrhea, genital herpes, chlamydia, trichomoniasis, syphilis, and acute HIV. Several of these are frequently silent — you can be infected and feel completely fine, so timing alone never confirms a diagnosis. Below is the tell-tale pattern for each, then how a clinician separates them.
Which STIs cause symptoms in the days and weeks after exposure
Gonorrhea
Gonorrhea is caused by the bacterium Neisseria gonorrhoeae, which can infect the genitals, rectum, and throat CDC. In men it classically produces burning with urination and a white, yellow, or green penile discharge; less often, swollen or painful testicles. Most women have no symptoms, but when they do, there's painful urination, increased vaginal discharge, or bleeding between periods. A precise symptom-onset window isn't stated on the official CDC or USPSTF pages reviewed, so don't anchor to a specific day count. If you have discharge or burning, get checked rather than waiting it out.
Genital herpes
Genital herpes comes from herpes simplex virus type 1 (HSV-1) or type 2 (HSV-2) CDC. Most people have no or very mild symptoms, and the majority of HSV-2 infections go undiagnosed. A true first outbreak is the dramatic exception: blisters that break into painful sores taking a week or more to heal, often with flu-like symptoms — fever, body aches, swollen glands. The sores can appear on or around the genitals, rectum, or mouth. Repeat outbreaks are shorter and milder, and many people feel a prodrome — tingling or itching — beforehand. The interval from exposure to first lesions isn't specified on the current CDC clinical pages reviewed.
Chlamydia
Chlamydia is caused by Chlamydia trachomatis and is famously a 'silent' infection — roughly three quarters of infected women and half of infected men notice nothing CDC. When symptoms do appear, they usually show up within one to three weeks of exposure: abnormal vaginal discharge or burning on urination in women. If it climbs into the upper reproductive tract, it can cause lower-abdominal or low-back pain, fever, pain during sex, and bleeding between periods — signs of possible pelvic inflammatory disease, which can scar the fallopian tubes and threaten fertility. Because the bug is so often quiet, a clear test now doesn't rule out a future flare, and re-testing after treatment matters; see chlamydia reinfection.
Trichomoniasis
Trichomoniasis is caused by the protozoan parasite Trichomonas vaginalis and is the most common curable STI CDC. About seventy percent of people have no signs at all. When symptoms do occur, they may appear five to twenty-eight days after infection, though they can also surface much later. Women may notice itching, burning, redness or soreness of the genitals, discomfort urinating, and a clear, white, yellowish, or greenish discharge with a fishy smell. Men are commonly asymptomatic but can have itching inside the penis, burning after urinating or ejaculating, and discharge.
Syphilis
Syphilis is caused by Treponema pallidum and moves in stages CDC. The primary chancre — one or more painless, firm, round sores at the site of infection (penis, vagina, anus, rectum, lips, or mouth) — typically appears about three weeks after exposure, within an incubation range of ten to ninety days. It lasts three to six weeks and heals on its own with or without treatment, so people miss it. If untreated, the secondary stage follows with a rough red or reddish-brown rash that can appear on the palms and soles, along with mucous-membrane lesions, fever, swollen lymph nodes, sore throat, patchy hair loss, headache, weight loss, muscle aches, and fatigue. A painless sore is the detail that should send you in. Pain is what makes people seek care, and syphilis withholds it.
HIV
HIV attacks the immune system and progresses through acute, chronic (clinical latency), and AIDS stages CDC. Within two to four weeks after infection, many people develop flu-like acute retroviral syndrome — fever, chills, rash, night sweats, muscle aches, sore throat, fatigue, swollen lymph nodes, and mouth ulcers hiv.gov. Some have no symptoms at all, and these features are easily mistaken for any viral illness. During the acute phase the viral load is very high and the person is highly contagious, one reason starting treatment promptly matters for both health and onward transmission; more on that under earlier hiv treatment can help prevention. After the acute window, years can pass without symptoms before disease progresses.
How to tell them apart
Usually you can't, not by eye. The symptoms overlap heavily, and the most common 'symptom' across all of them is no symptom. A few features point in a direction: a painless firm sore leans syphilis; clustered painful blisters that ulcerate lean herpes; thick penile discharge with burning leans gonorrhea; a frothy, fishy-smelling discharge leans trichomoniasis; a flu-like illness two to four weeks out raises acute HIV. But each of these has exceptions, and several infections travel together. What discriminates them is a test, not a closer look.
Side-by-side comparison
| Infection | Typical timing after exposure | Tell-tale pattern | Often silent? |
|---|---|---|---|
| Gonorrhea | Not fixed on CDC pages reviewed | Burning urination; yellow/green discharge | Very often in women |
| Genital herpes | Not specified on current CDC pages | Painful blisters/sores; first outbreak flu-like | Yes — most undiagnosed |
| Chlamydia | 1–3 weeks if symptomatic | Discharge, burning urination; often none | Yes — most cases |
| Trichomoniasis | 5–28 days, sometimes later | Itching; frothy fishy-smelling discharge | Yes — about 70% |
| Syphilis | Chancre ~3 weeks (range 10–90 days) | Painless sore, then palm/sole rash | Easily missed |
| HIV (acute) | Flu-like at 2–4 weeks | Fever, rash, sore throat, swollen nodes | Sometimes none |
How it's tested
For most of these, a nucleic-acid amplification test (NAAT) on urine or a self-collected swab is the standard — it's the preferred method for chlamydia CDC, 2021, the gonorrhea test of choice with sensitivity usually above ninety percent, and the preferred method for trichomoniasis testing & diagnosis. Herpes is confirmed by swabbing an active lesion with type-specific NAAT or culture CDC. Syphilis needs two blood tests — a nontreponemal test (RPR or VDRL) plus a treponemal test (TP-PA, FTA-ABS, EIA, or CIA) CDC, 2024. HIV uses a NAT, a 4th-generation antigen/antibody lab test, or an antibody/rapid test, each with its own window CDC. In practice that's a urine cup, a quick swab, or a finger-stick or blood draw, with results usually back in a few days. You can get tested free or at low cost through health departments, Planned Parenthood, and Title X clinics.
What to do next
If you have symptoms, get evaluated — don't try to match yourself to a list. If you were exposed but feel fine, time your test to the right window so a negative actually means something; a too-early test can miss a real infection. See when to test after exposure to plan it. All six of these are treatable, and most are curable with the correct antibiotics or antiparasitic; herpes and HIV are managed long-term rather than cured, and herpes has several options worth discussing — including alternative herpes treatments. Pregnant people need particular attention to syphilis because of the risk to the baby; read more on syphilis in pregnancy.
Red flags — when to get seen urgently
- Severe lower-abdominal or pelvic pain with fever — possible pelvic inflammatory disease, which can damage fertility.
- A new painless sore or ulcer anywhere on the genitals, anus, or mouth — get syphilis ruled out.
- Swollen, very painful testicle — possible infection that needs prompt treatment.
- A spreading rash on the palms or soles, especially with fever and swollen glands.
- Inability to urinate, or severe pain with widespread blisters during a first herpes outbreak.
- Flu-like illness two to four weeks after a known high-risk exposure — ask specifically about acute HIV testing.