The annual report by the Centers for Disease Control and Prevention, "Sexually Transmitted Disease Surveillance, 2007," shows persistent racial disparities across these and other sexually transmitted diseases. The report found that there were more than 1.1 million chlamydia cases reported in 2007, up from about 1 million in 2006.

The report also said that syphilis -- a disease once on the verge of elimination, but re-emerged as a threat in 2001 -- increased 15.2 percent from 2006 to 2007.

The report also found that women continue to bear a disproportionate burden of the long-term health consequences of STDs. In 2007, the chlamydia rate among women was three times that of men -- 543.6 cases per 100,000 women, compared to 190 cases per 100,000 men. The gonorrhea rate was also higher among women -- 123.5 per 100,000 women, compared to 113.7 per 100,000 among men.

"The widespread occurrence of these diseases should serve as a stark reminder that STDs remain a serious health threat in the United States, especially for women and racial and ethnic minorities," Dr. John M. Douglas, Jr., director of CDC's Division of STD Prevention.

"Left untreated, chlamydia and gonorrhea can cause infertility, affecting a woman's chance to bear children later in life -- a severe consequence that is entirely avoidable."