Chlamydia (bacterial)
What the screen detects. A chlamydial antigen — a marker of the bacteria currently present.
What happens after exposure. The bacteria enter cells lining the genital tract and begin multiplying. In the first few days there is too little to detect. Over roughly one to two weeks the organism load rises to a level a screen can reliably pick up. Symptoms, when they occur, tend to appear within one to three weeks — but most infections cause no symptoms at all, which is exactly why screening matters.
Timing (general guidance). Earliest preliminary screen around 1 week; reliable from about 1–2 weeks. After treatment, a retest at around 3 months is commonly advised to check for reinfection.
Gonorrhea (bacterial)
What the screen detects. A gonococcal antigen — a marker of the bacteria currently present.
What happens after exposure. The bacteria establish and multiply at the site of contact. Symptoms such as discharge or discomfort can appear quickly — often within two to seven days — but a symptom is not the same as a reliably detectable result, and many people (especially with throat or rectal infection) have no symptoms.
Timing (general guidance). Earliest preliminary screen around 1 week; reliable from about 1–2 weeks.
Note: A genital screen does not detect throat or rectal infection. If you had oral or anal exposure and want full coverage, a clinic can perform site-specific testing.
Syphilis (bacterial)
What the screen detects. Treponemal antibodies — your immune response to the bacteria.
What happens after exposure. In the first week to ten days the bacteria multiply quietly at the entry site, before your body has produced antibodies. A painless sore (chancre) can appear at the site anywhere from about 10 to 90 days after exposure, often around week three. Antibodies begin to develop from roughly two to five weeks, so a screen may turn positive from about three weeks — but a meaningful share of very early infections still test negative at that point.
Timing (general guidance). Earliest preliminary screen around 3 weeks; reliable for most people by about 6 weeks; repeat a negative early result at around 3 months.
Note: If you have a visible sore, see a clinician promptly — direct testing of the lesion is faster and more informative than an antibody screen in the first weeks.
Hepatitis B (viral)
What the screen detects. Hepatitis B surface antigen (HBsAg) — a protein on the virus that signals a current infection.
What happens after exposure. The virus travels to the liver and replicates. Surface antigen can appear in the blood as early as one to two weeks in some people, with an average around four weeks, and occasionally as late as nine to twelve weeks. Symptoms, when they occur, usually come much later — often two to three months after exposure — and many people never notice them. Over the course of infection the body produces a sequence of markers: surface antigen first (current infection), then core antibodies, and later surface antibodies (which signal recovery or immunity). Our screen detects the surface antigen.
Timing (general guidance). Earliest preliminary screen around a few weeks; reliable for most by about 6 weeks; a confirmatory retest around 9–12 weeks covers slower cases.
Herpes (viral)
What the screen detects. HSV antibodies (IgG/IgM) — your immune response to the virus.
What happens after exposure. The virus replicates at the site of contact, then retreats to nerve cells where it stays dormant and can reactivate later. A first outbreak, if it happens, can appear within about two to twelve days — but many people never have a recognized outbreak. Antibodies take considerably longer to build: detectable levels usually develop over about twelve to sixteen weeks, which is why herpes has one of the longest windows of the common infections.
Timing (general guidance). Antibody detection can take 6–16 weeks, with 12 weeks a common point to retest. An antibody screen cannot identify an active sore or its location — for a visible lesion, a clinician’s swab is faster and more informative.
Note: Antibody screening is most useful for people with symptoms or a known exposure; routine screening of everyone without symptoms is not recommended, and low-level positive results should be discussed with a clinician.
