LOS ANGELES, Jan. 14 (Xinhua) -- Rates of two sexually transmitted diseases (STD) -- chlamydia and syphilis -- are on the rise in the United States, according to a report appearing on the Los Angeles Times website on Wednesday.

    Chlamydia infections now top 1.1 million, more than ever recorded, while syphilis cases are up for the 7th year in a row, said the report presented by the Centers for Disease Control and Prevention (CDC).

    Cases of gonorrhea, which peaked in the 1970s at about 1 million and then dropped for years, remain flat at 355,991, frustrating goals set by public health leaders, according to the report.

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

    "But more alarming is the continued rise of syphilis, a still rare but more serious STD," the report noted.

    Cases of syphilis rose in 2007 to 11,466, or 3.8 cases per 100,000 people. That is a 15-percent increase from 2006 and represents yet another increase after a decade of decline in the 1990s, said the report.

    The report attributed the rise to a dramatic jump in infections among gay and bisexual men. Men who engaged in homosexual sex made up 65 percent of the 11,466 cases reported in 2007, roughly the same as in 2006, said the report.

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

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

    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.

    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.