This is one of the most common STDs around the place, so it's kind of like potatoes in an irish kitchen, meaning EVERYWHERE! Chlamydia is very dangerous because it often has no symptoms and if it's left untreated it can cause serious problems in later life (you know, when you grow out of the 'party til you vomit in your hair' lifestyle!) This is why it's called the 'silent' disease.
Those of us women who DO have symptoms often experience:
An increase in vaginal discharge, the need to leg it to the bathroom to pee more frequently, burning stabby sensation when urinating, pain during sex, irregular bleeding during your period or bleeding after sex and pains in your lower abdomen. (Check that one twice though, you could just be having a bit of bother digesting a curry!)
Chlamydia can also, if left untreated, leave women infertile if the fallopian tubes become scarred. This is very serious and irreversible so take the time for an STD test.
Men have more noticeable symptoms than women so it's much easier to diagnose, these include:
A white/cloudy and watery discharge from the penis that may stain underwear (as if it's not stained enough already...), a burning sensation when peeing and pain or swelling in the balls (testicles, just to be scientific).
It can be transmitted by having unprotected vaginal, anal or oral sex with someone who is infected.This disease is an excellent example of why you should always go to a health clinic regularly, make a point of doing it twice a year on principle and if you have any itchy itchies going on down there ASSUME it is not a good thing and get your ass to the doctors!