Nov. 13, 2007 -- With nearly 3 million new chlamydia infections a year and drug-resistant gonorrhea on the rise, a new CDC report offers a grim view of sexually transmitted diseases (STDs) in America.

The report shows that STDs are on the rise across the U.S. Southern states are particularly affected, although sharp increases in Western states also raise eyebrows.

Overall, 19 million Americans catch an STD every year. Half of these infections are in people aged 15 to 24. At particular risk are teenage girls and young women, African-Americans, and men who have sex with men.

"STDs represent a substantial threat to Americans," John M. Douglas Jr., MD, director of the CDC's Division of Sexually Transmitted Disease Prevention, said at a news conference held to announce the findings.

The CDC report focused on three very troubling STDs: chlamydia, gonorrhea, and syphilis. All of these infections can be cured -- if they're detected. But most people carrying and spreading these infections don't even know they have them.

In the case of HIV, that could be fatal. But all of these diseases can cause permanent damage if left untreated. For example, untreated chlamydia -- the most common reportable infection in the U.S. -- can rob a woman of her fertility.

"Very few young, sexually active women are actually aware that annual chlamydia screening is recommended, and that the disease is linked to compromises in fertility," Stuart Berman, MD, chief of epidemiology and surveillance for the CDC's STD branch, said at the news conference.