A new study of young female military recruits has found that almost 20 percent contracted chlamydia over the course of 12 months.

“The really scary message for us is, oh my God, they’re getting it again and again,” Dr. Mary-Ann B. Shafer of the University of California, San Francisco, told Reuters Health.

“This goes beyond women in the military,” she added. “This is a real, live population, this is probably what’s really going on in young women.”

Chlamydia usually doesn’t cause symptoms, and if left untreated can infect the uterus and fallopian tubes, causing pelvic inflammatory disease. This can in turn cause chronic pelvic pain and infertility, and increase a woman’s vulnerability to contracting HIV.

To get a better sense of how common the infection is among a general population of women, Shafer’s team followed 332 young, sexually active female Marine recruits for a year.

Eleven percent had chlamydia when they began recruit training, and were treated for the infection, Shafer and her colleagues note in their report in the medical journal Sexually Transmitted Diseases.

At the second screening point, about four weeks after the women had graduated from training, 3.6 percent tested positive for chlamydia, and were treated. The third screening, roughly a year after the women graduated from basic training, detected new untreated infections in 9.9 percent.

In between the second and third screenings, 8.1 percent of the women had been diagnosed with chlamydia and treated, according to results of a survey.

Adding all those percentages, and allowing for multiple infections in the same women, gave an acquisition rate over the course of a year of 19.9 percent.

While US health authorities recommend universal screening for chlamydia among young sexually active women, Shafer noted, studies show just half are actually getting the test.

The findings make it clear, she added, that annual screening isn’t enough. “Every time they come in, basically, if they’ve had a new partner, they should get screened,” she said.

All of the women in the current study had health care through the military, Shafer pointed out. However, US women between 18 and 25 are actually the least-insured of any age group, the researcher noted, while they engage in the most risky behaviors and need the most preventive care - including screening for chlamydia. “It’s another kind of sign of the cracks in the way the US healthcare system is delivered,” she said. “It’s missing preventive health care big time in this population.”

SOURCE: Sexually Transmitted Diseases, March 2008.