Sexually Transmitted Infections

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The single most important fact about sexually transmitted infections is that most of them produce no symptoms at all, in either partner, for as long as they are present.

That is not a caveat. It is the whole reason they spread. An infection that announced itself would be treated; population screening programmes would be unnecessary because people would simply turn up. The asymptomatic period is not a quiet phase before the real illness, for a great many people it is the entire course of the infection.

Which means “I feel fine” is not information about your status. It never has been. Testing is the only method, and it has to be timed correctly, because every test has a window period during which an infection is present but not yet detectable. A test taken the morning after an exposure tells you about the exposure before that one.

What the evidence supports

Chlamydia and gonorrhea are usually asymptomatic in women and frequently asymptomatic in men. This is the US Preventive Services Task Force’s own summary of the evidence, and it is why screening exists as a programme rather than a response to complaints.

Timing determines whether a test means anything. Chlamydia and gonorrhea are detectable at roughly a week. Syphilis takes about a month. HIV antigen/antibody testing catches most infections by two weeks and almost all by six. Hepatitis C can take months. Testing inside the window produces a negative result that carries no information.

A urine test only tests your urethra. Chlamydia and gonorrhea infect the throat and rectum too, those infections are usually symptomless, and they are missed entirely by a urine sample. If oral or anal sex is part of your life, those sites need their own swabs, and you will usually have to ask.

A standard panel does not normally include herpes. Blood testing for HSV is not recommended as routine screening for people without symptoms, because the result is hard to interpret and says little about transmission. If you assumed “the full works” covered it, it generally does not.

Condoms work, but not equally against everything. They are highly effective against infections transmitted in fluids and less so against those transmitted by skin contact, which can occur outside the covered area. That distinction is the useful part.

Which article you need

If you are trying to work out whether you might have something, how to know if you have an STI covers the symptoms worth acting on, the window periods in a table, and what a test does and does not include.

If you want to know how often to test and what to ask for, the actual testing schedule sets out the CDC intervals by risk profile.

If you want to understand what protection you are actually getting, what condoms protect against separates the fluid-borne infections from the skin-contact ones.

And if a result has come back positive, the next problem is usually a conversation rather than a medical one. How to tell a partner covers the options, including the ones that do not require you to do it yourself.

And if you have seen doxy-PEP discussed and want to know whether it applies to you, what the doxy-PEP evidence actually shows lays out the four randomised trials, the CDC recommendation, and why heterosexual men are not in it.

What else is worth reading

HIV screening at least once between 15 and 65 is a Grade A recommendation, and hepatitis C screening once in adulthood is Grade B. Both sit on the wider screening list alongside the tests that have nothing to do with sex.

Pre-exposure prophylaxis for HIV is also a Grade A recommendation for people at increased risk, and it is worth raising with a clinician rather than waiting to be offered it.

If a new symptom is genital but you are fairly sure it is not an infection, the erectile dysfunction section and the guidance on when a change warrants a doctor may be more relevant.

One thing worth stating plainly on a men’s health site: in men, untreated chlamydia and gonorrhea are usually a minor event. In female partners they can cause pelvic inflammatory disease, ectopic pregnancy and infertility. The asymmetry is a reason to test even when nothing feels wrong.