Rates of chlamydia, syphilis on the rise in U.S.

Gonorrhea rates did not increase, but they ceased falling a few years ago, frustrating goals set by public health leaders.

Chlamydia infections in the United States now top 1.1 million, the most since record-keeping for the disease began and the most for any STD that doctors are required to report, according to 2007 data, the latest available.

Cases of gonorrhea, which peaked in the 1970s at about 1 million and then dropped for years, remain flat at 355,991, according to the CDC report. The disease is the second-most common STD for which data are collected by law.

Women bear the brunt of both chlamydia and gonorrhea, especially their long-term consequences, CDC officials said.

Untreated, both can lead to pelvic inflammatory disease -- an infection of the uterus and fallopian tubes that can cause chronic pain, infertility and life-threatening ectopic pregnancy, or pregnancy outside the uterus.

Chlamydia and gonorrhea "lead to tremendous problems in our female population, with fertility leading the list," said Dr. John M. Douglas Jr., director of the CDC's Division of STD Prevention.

Infection with the bacterium Chlamydia trachomatis can cause a discharge from the vagina or penis and a burning sensation when urinating, but often does not. Although the consequences are most severe for women, in men, an untreated infection can spread to the epididymis -- the tube that carries sperm from the testes -- causing pain, fever and, rarely, sterility.

The report found that chlamydia infections occurred at a rate of about 370 per 100,000 people in 2007. That's a 7.5% increase from 2006.

Part of that increase may be due to better detection, Douglas said. More people, especially women, are being screened, and a more sensitive test is now in use.

Even so, many people with the disease are not identified, and public health officials believe that the true number of chlamydia infections is closer to 3 million. Young men especially often don't go to the doctor and thus never learn of their infection, but continue to infect their partners, said Linda M. Niccolai, an epidemiologist at Yale School of Public Health.