Chlamydia is the common name for a type of sexually transmitted infection (STI). It is caused by the bacterium called Chlamydia trachomatis that is spread by having sexual contact (vaginal, anal or oral sex) with an infected individual. This bacterial strain then resides in the cervix or vagina of a woman or in the urethra and rectum of both men and women. Chlamydia can be transmitted from one person to another via unprotected sexual contact or even by touching the genitals of someone who already has the disease. Aside from sexual contact, other risk factors include age, being diagnosed with another STI in the past, having another infection and number of sexual partners.
Chlamydia is one of the most common sexually transmitted diseases, yet people tend to know less about it than syphilis and gonorrhoea. Women are more likely to suffer severe health consequences as a result of the infection. But many doctors who treat sexually active young women are not screening for the disease. Untreated, chlamydia may spread into the womb and fallopian tubes, leading to pelvic inflammatory disease (PID), ectopic pregnancy and infertility. Preliminary evidence has linked chlamydia infection with increased cervical cancer risk. Infection with chlamydia may also increase the risk of being infected with HIV, the virus that causes AIDS. Chlamydia may also be transmitted during childbirth; a mother who has chlamydia may pass on the disease to her child when the baby passes through the vaginal canal. Eye damage and pneumonia are known side effects of chlamydia infection in newborns. Rectal or genital chlamydial infections may also continue for up to one year for an infant who has been infected by chlamydia at birth. If left untreated in a man, sexually transmitted chlamydia can result in epididymitis (pain and inflammation in the epididymis) or the spread of the infection to the prostate gland, triggering fevers, painful intercourse and lower back pain.
Western countries are experiencing a chlamydia epidemic. According to the UK Public Health Laboratory Service, the number of diagnosed infections soared by 76% between 1995 and 1999 with a 14% increase in infections in the single year between 1998 and 1999. Infection rates in 1999 were highest in London, where they reached 155 per 100,000 men and 184 per 100,000 women. Doctors believe the number of known infections represent only about 10% of all cases. Chlamydia remains the most common STI in the UK: in a Health Protection Report by Public Health UK published June 2015, there were 206,774 diagnosed cases of chlamydia. These account for 47 percent of new STI cases in the country, the highest incidence rate when compared to genital warts, gonorrhea and genital herpes. Of these cases. 138,000 were among people aged 15 to 24 years old. Approximately 70% of women infected with chlamydia have no symptoms until more serious consequences arise. Over 50% of women with PID have had chlamydia, the sexually transmitted disease most likely to cause tubal damage. The 21-25-year age group is at the highest risk of contracting the disease. A 1993 UK report found only 7% of the 1,600 people surveyed had heard of chlamydia.
Statistics from the US Centers for Disease Control and Prevention (CDC) reported 1.6 million cases of chlamydia in 2016, up from 1.4 million reported cases of chlamydia. Young people aged 15 to 24 years old accounted for about two-thirds of these cases and it is said that 1 in 20 sexually active young women of the same age group already have chlamydia. Infants born to women with untreated chlamydial cervical infection had chlamydial conjunctivitis or the redness and swelling in the clear membrane of the eyes (18 to 44 percent of infants) and chlamydial pneumonia (3 to 16 percent of infants). If left untreated, 20% to 40% of women with chlamydia will go on to develop pelvic inflammatory disease, which can cause infertility and chronic pelvic pain. The infection often goes undetected, because most women with chlamydia have no symptoms. Two out of three primary care physicians surveyed did not screen sexually active teenage women for chlamydia.
On-going chlamydia infection may influence an individual's ability to fight off human papillomavirus (HPV) infection which causes cervical cancer.