Chlamydia

What it is. Chlamydia is one of the most common sexually transmitted infections (STIs). It is caused by a tiny germ (a bacteria) that can infect the genitals, the back passage (rectum), or the throat. It spreads through vaginal, anal, or oral sex.

How you'd know. Most people with chlamydia feel completely fine — there are often no symptoms at all. That is exactly why testing matters. If symptoms do show up, they can include unusual discharge, burning when you pee, pain during sex, bleeding between periods, or pain and discharge in the rectum.

How it's tested. Testing is simple and does not usually need a physical exam. It is most often a urine sample (you pee in a cup) or a swab you can collect yourself. If you have had anal or oral sex, a swab of the rectum or throat can be added. A test is reliable about two weeks after the last time you might have been exposed.

Is it curable? Yes. Chlamydia is cured with a short course of antibiotics. Avoid sex (or use condoms every time) until 7 days after treatment is finished, and until your partners are treated too, so you don't pass it back and forth.

What if it's not treated? Left untreated, chlamydia can quietly cause problems — in women it can lead to pelvic inflammatory disease, which can cause long-term pelvic pain, a dangerous "tubal" (ectopic) pregnancy, or trouble getting pregnant later. It can also cause swollen, painful joints (reactive arthritis).

What about partners? Anyone you have had sex with recently should be told so they can be tested and treated — even if they feel fine. The clinic can help you do this, and it can be done privately. Getting a repeat test 3 to 6 months later is a good idea, because catching it again is common.