Women aged 16 to 19 are 43% more likely to test positive for Chlamydia than women in their early twenties, show data from the first year of the Chlamydia screening programme in England, reported in Sexually Transmitted Infections.
But men in their early twenties are more than twice as likely to test positive for the infection as younger men.
The National Chlamydia Screening Programme is being phased in across England. The programme officially started in April 2003, and full coverage is expected by 2008.
During the first year of its operation, from April 2003 to the end of March 2004, 16,413 young men and women were screened opportunistically at 302 venues, excluding genitourinary medicine clinics, across the first 10 programme areas in England.
One in 10 women (10.1%) and one in eight men (13.3%) under the age of 25 tested positive for the infection during this period.
Women aged 16 to 19 were 43% more likely to test positive than women aged 20 to 24. But older men were twice as likely to test positive as 16 to 19 year old men.
Almost half (44%) of the women tested for Chlamydia reported having a new sexual partner in the preceding three months and/or two or more sex partners in the previous year.
Over half the men tested had had a new sexual partner in the preceding three months, and 60% reported two or more sexual partners in the previous year.
Most of the women were screened at contraceptive/family planning clinics; less than half the men were screened at these venues. One in four men were screened at colleges and universities, and these men were less likely to test positive than those tested at contraceptive/family planning clinics. One in 10 tests were carried out in family doctor surgeries.
The authors conclude that rates of infection with Chlamydia were similar to those found in screening pilots and are comparable with first year screening figures from Sweden and the USA.
A second study in the same issue, also from the Communicable Disease Surveillance Centre at the Health Protection Agency, found considerable variations in Chlamydia prevalence, depending on who was tested and where the testing was carried out.
The researchers based their findings on an analysis that assessed the reported prevalence of Chlamydia infection in the United Kingdom, based on 19 published studies identified through a systematic review.
Detailed analysis of the data showed clear patterns of Chlamydia prevalence, according to age and test site. This was despite the differences in test methods used. Few studies were identified that reported Chlamydia prevalence in men or the general population, however.
The prevalence in female general practice patients under the age of 20 was around three times as high as in those aged 25 to 29, and around six times as high in those over 30. Prevalence figures in women were 8.1%, 2.6%, and 1.4%, respectively.
But figures from specialist clinics were much higher. Among women under 20, reported rates were as high as 17.3% in genitourinary clinics, and they exceeded 12% in antenatal and abortion clinics. Rates in family planning clinics were around 10%.
Chlamydia is diagnosed in 35,500 men and 45,500 women in England and Wales each year, doubling the figures from 1997. About 4 million cases of chlamydia occur in the USA each year. However, about half of all men and three-quarters of all women who have chlamydia have no symptoms and don't know that they have the disease. The disease is transmitted by the Chlamydia trachomatis bacterium. It can be serious but it is easily cured if detected in time.
Almost half of all women who get chlamydia and aren't treated by a doctor will get pelvic inflammatory disease (PID), a generic term for infection of the uterus, fallopian tubes, and/or ovaries. PID can cause scarring inside the reproductive organs, which can later cause serious complications, including chronic pelvic pain, difficulty becoming pregnant, ectopic (tubal) pregnancy, and other dangerous complications of pregnancy. Chlamydia causes 250,000 to 500,000 cases of PID every year in the U.S.
In women, chlamydia may not cause any symptoms, but symptoms that may occur include: unusual vaginal bleeding or discharge, pain in the abdomen, painful sexual intercourse, fever, painful urination or the urge to urinate more frequently than usual.
In men, chlamydia may not cause any symptoms, but symptoms that may occur include: a painful or burning sensation when urinating, an unusual discharge from the penis, swollen or tender testicles, or fever.
Chlamydia in men can spread to the testicles, causing epididymitis, which can cause sterility. Chlamydia causes more than 250,000 cases of epididymitis in the USA each year.
Chlamydia may also cause Reiter's Syndrome, especially in young men. About 15,000 men get Reiter's Syndrome from chlamydia each year in the USA, and about 5,000 are permanently affected by it.