Chlamydia is an infection caused by the bacterium Chlamydia trachomatis (C. trachomatis). It is sexually transmitted, but it can also be transmitted from a mother with the infection to her baby during birth.

The symptoms of chlamydia are usually absent or mild however, the infection can cause complications and can irreversibly affect fertility if it is not treated.

C. trachomatis can cause pneumonia in babies up to 3 months old. The source of the infection is usually the bacteria found in and around the mother’s birth canal. Half of all children who have C. trachomatis pneumonia will also have conjunctivitis (an eye infection also known as 'pink eye').

Chlamydia infection is diagnosed from a urine specimen or a sample collected from the penis or cervix.

Chlamydia is easily treated with antibiotics.