TUESDAY, May 11 (HealthDayNews) - More than one in 25 young women and men in the United States are infected with the bacterium that causes the sexually-transmitted disease chlamydia. Rates of infection are alarmingly high among young Black women (almost 14%) and young Black men (more than 11%), a new study found. The research also found a much lower overall prevalence of gonorrhea - 0.43%. Among Black men and women, however, the rate is 2.13%. The study appears in the May 12 issue of the Journal of the American Medical Association. Chlamydia usually has no symptoms in its early stages. But if left untreated, it can cause pelvic inflammatory disease, ectopic pregnancy and infertility in women, and may even be linked to cervical cancer. In men, it can lead to pain or swelling in the scrotal area, and possibly sterility. Being infected with chlamydia may also increase the ability to transmit and to get HIV, federal health officials report. "Chlamydia is just such a low-grade infection that causes long-term problems and it's so easy to treat," said Dr. Ralph Dauterive, chief of obstetrics and gynecology at the Ochsner Clinic Foundation in New Orleans. "You take some doxycycline [an antibiotic] for 10 days. It's pretty easy to do." The problem, Dauterive added, is that it's "a quiet little infection. Chlamydia is out there and no one seems to know anything about it." Previous research on the prevalence of chlamydia had shown similarly high rates. But because those earlier studies were based on people seeking help in a clinic, experts couldn't be sure they were representative of the population at large, explained study author Dr. William C. Miller. "Almost all of our prior information had been in clinics. They were coming in and getting tested and treated. In this case, we were going out to them," added Miller, an assistant professor of medicine and epidemiology at the University of North Carolina Schools of Medicine and Public Health. The researchers did at-home interviews with 14,322 men and women aged 18 to 26 across the United States. Most of the participants - 12,548 - also gave urine samples that were then tested for evidence of chlamydial and gonococcal infections. Overall, the prevalence of chlamydial infection was 4.19%, and was more common among women (4.74%) than among men(3.67%). Prevalence was also more than twice as high in the South (5.39%) than in the Northeast (2.39%). More striking were variations by race and ethnicity. Young white adults had the lowest prevalence (1.94%) while young Black adults had almost six times that rate (12.54%). In young Hispanic adults, the prevalence was 5.89%. The highest prevalence was among Black women (13.95%), followed by Black men (11.12%). Asian-American men had the lowest prevalence (1.14%), followed by white men (1.38%) and white women (2.52%). The overall prevalence of gonorrhea was 0.43%. Among Black men and women, the prevalence was 2.13%. Among white adults, it was 0.10%. About 0.03% of those interviewed were infected with both chlamydia and gonorrhea. "The vast majority of these people had no idea they were infected," Dr. Miller said. "So consequently, they have no trigger to seek health care. Or, if they had symptoms previously, they were short-lived and mild. That implies that we need to do a better job of screening." At present, women tend to be screened for sexually-transmitted disease more than men, partly because it is part-and-parcel of infertility screening. Also, women show up for routine exams more often than men, Dr. Miller said. "One of the things we hope this study will help encourage is, it really takes two for these kinds of diseases and treating one part of the pathway won't help us reduce the prevalence." It's also important to take cautious note of the racial disparities, Dr. Miller added. "If we politicize it, then we'll not target therapy to people who really need it. And we really, really need to be screening and treating in order to reduce the disparity, and the only way to do that is to acknowledge it exists," he said. The rise and fall of chlamydia rates often mimic the rise and fall of different political climates, said Dr. Kenneth A. Levey, director of the Chronic Pelvic Pain Center at New York University Medical Center in New York City. "One of the reasons for the high prevalence of chlamydia and STDs (sexually-transmitted diseases) in general in this age group is lack of educational programs. And I think that political tides turn the availability of condoms in high school," he added. "Chlamydia is still high in this country, and it's a very, very preventable disease. There's no reason why anybody should have chlamydia. All it takes is a very simple use of condoms." For more information on chlamydia, visit the National Institutes of Health (www.niaid.nih.gov ) or the American Social Health Association (www.ashastd.org ). SOURCES: William C. Miller, M.D., Ph.D., assistant professor, medicine and epidemiology, University of North Carolina Schools of Medicine and Public Health, Chapel Hill; Ralph Dauterive, M.D., chief, obstetrics and gynecology, Ochsner Clinic Foundation, New Orleans; Kenneth A. Levey, M.D., director, Chronic Pelvic Pain Center, New York University Medical Center, and assistant professor, obstetrics and gynecology, New York University School of Medicine, New York City; May 12, 2004, Journal of the American Medical Association.