What is chlamydia?

Often referred to as the silent epidemic, chlamydia - aka the clam, gooey stuff and clap slap - is the most common STI among under-25s. Since 1999, reported cases have doubled, and in 2008 there were a record 123,018 new diagnoses in GUM clinics. The Family Planning Association (FPA) estimates that one in 10 sexually active young people are currently infected.

Find out how Ben & Rosie get on when they get checked out for chlamydia.

Caused by a tiny bacterium, Chlamydia trachomatis, chlamydia is picked up and passed on through unprotected vaginal, oral or anal sex, as well as through sharing sex toys with an infected person. It affects both sexes, and can infect the cervix, urethra, anus, throat and, very rarely, the eyes.

Chlamydia was acknowledged as an STI in 1963 when it was recognised as a bacteria rather than a virus. However, unlike the more cringe-worthy bacterial STIs, such as gonorrhoea and syphilis, chlamydia was largely ignored over the decades due to its lack of obvious symptoms. As a result, many people went undiagnosed for years. Now, thanks to a nationwide Government screening campaign, everyone from your granny to your 10-year-old sister is aware of it, and the number of diagnoses has shot up.

What are the symptoms of chlamydia?

The scary fact is that most infected people won't have any symptoms. However, those who do develop symptoms will experience a stinging sensation when peeing, and men may have discharge from the penis and pain or tenderness in the testicles. For women, the obvious signs are cystitis, vaginal discharge, pain in the pelvis during sex and bleeding between periods. If the infection is caught from anal sex, there can also be pain and discharge from the anus for either gender.

While these symptoms can present themselves within the first three weeks of infection, they can stay hidden for months, if not years.

What does the discharge look like?

If you have it, the discharge varies from being milky white and odourless to yellowish and smelly.

How is chlamydia treated?

It's important to know that chlamydia is a common STI, and diagnosis and treatment is straightforward. Go to your nearest genitourinary medicine (GUM) clinic, or make an appointment to see your doctor (GP). If you really can't face anyone, you can also test yourself at home.

In the surgery or clinic, you'll either be asked to produce a urine test or the GP will take a swab. For women this will be taken from the vagina and men from the tip of the penis. If you've had anal or oral sex, the GP may take a swab from your anus or throat. The samples will be sent to the lab or examined by the doctor under a microscope, which will give you the results straight away.

If you're taking the DIY diagnosis route and you're under 25, your local primary healthcare trust may send you a testing pack in the post for free. You send a urine sample to a laboratory for testing, and you receive the results by post.

Treatment is a course of antibiotics. This can be prescribed by your GP, or you can buy the over-the-counter drug azithromycin, sold as Clamelle.

While you may not want to shout it from the rooftops, it's important to inform any sexual partners to avoid re-infection. Chances are they'll need to be tested and be put on a course of antibiotics, too.

What if I ignore it?

Ignoring it - or even the possibility you might have it - can lead to some pretty serious health issues, especially in women. The mildest of these is cervicitis, which is an inflammation of the cervix, and the worst-case scenario is pelvic inflammatory disease (PID). This painful infection of the uterus can damage the fallopian tubes and leave a woman infertile. In some cases, women with untreated PID suffer a ruptured organ in much the way an appendicitis sufferer might. This can be fatal. Contracting chlamydia during pregnancy may also be linked to early miscarriage and premature birth.

For men, leaving it untreated may lead to a painful infection in the testicles and can sometimes reduce fertility. Babies born to a woman with chlamydia may also be born with the infection, causing eye damage or pneumonia.

How do I protect myself from contracting Chlamydia?

Using a condom during any kind of sex - vaginal, anal, oral or playing with sex toys - will prevent transmission of chlamydia. However, it won't protect you if the 'glove was off' during foreplay and you touch your eyes or genitals, so while it may sound deeply unsexy to do so, it's important to wash your hands afterwards to prevent the spread of infection.

How soon can I have sex again?

Don't be fooled by the fact that you have no symptoms, make sure you've completed your medication and got the all clear from your GP before you have sex again. Most doctors will recommend abstaining from sex for at least seven days while undergoing treatment.

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Updated: 09/12/2011