Chlamydia is a sexually transmitted infection (STI) caused by the bacterium chlamydia trachomatis. In the UK, the number of new diagnoses has been steadily increasing each year since the mid-1990s, and it has now become the most commonly diagnosed STI.

Chlamydia is called the ‘silent’ disease because most people who get it do not experience any noticeable symptoms. Around 50% of men and 70-80% of women who get the chlamydia infection will have no symptoms and many cases of chlamydia remain undiagnosed.

How common is it?

Between 2007 and 2008, the number of confirmed cases of chlamydia rose from 121,791 to 123,018. Young people under 25 are most likely to be infected, 65% (80,258) of all new chlamydia diagnoses made in 2008 were in people between the ages of 16 and 24.

Outlook

The chlamydia infection can be easily diagnosed through a simple swab or urine test, once diagnosed it can be treated with antibiotics. Undiagnosed chlamydia can lead to more serious long term health problems and infertility.

Under 25s can get a free, confidential chlamydia test through the National Chlamydia Screening Programme. People over 25 can visit their GP or a local GUM (genitourinary medicine) or sexual health clinic to arrange a test.