Atlanta -- More than 400,000 U.S. teen girls ages 15-19 were infected with the sexually transmitted diseases of chlamydia and gonorrhea in 2008, health officials say.

The annual report on sexually transmitted diseases released by the Centers for Disease Control and Prevention in Atlanta Monday found more than 1.5 million cases of chlamydia and gonorrhea were reported last year.

Left untreated, it is estimated that 10 percent to 20 percent of chlamydia or gonorrhea infections in women can result in pelvic inflammatory disease, which can lead to long-term complications, such as chronic pelvic pain, ectopic pregnancy -- a potentially life-threatening form of pregnancy where implantation of the fertilized egg occurs outside the uterus -- and infertility.

Untreated STDs are estimated to cause at least 24,000 U.S. women to become infertile each year, the report said.

Adolescent males have a similar prevalence of STDs, but biological differences place females at greater risk for STDs than males, the report said. African-Americans represent about 12 percent of the U.S. population, but accounted for about 71 percent of reported gonorrhea cases and almost half of all chlamydia and syphilis cases.

Chlamydia, gonorrhea and syphilis cases represent only a fraction of the true STD burden in the United States, the CDC estimates almost 19 million new sexually transmitted infections occur each year, almost half among 15- to 24-year-olds.