Chlamydia is one of the most common sexually transmitted infections (STIs) and is caused by a bacteria called Chlamydia Trachomtis. This infection is particularly common in sexually active teenagers and young adults as it passes from one person to the other through having unprotected sex (sex without a condom). Chlamydia affects both sexes, although women are more at risk. In 2014, approximately 250,000 cases of Chlamydia were reported in the UK.
The National Chlamydia Screening Programme announced in 2015 that all sexually active men and women under the age of 25 should be screened for Chlamydia annually at least.