One in six Americans aged 14 to 49 are infected with genital herpes, making the virus — herpes simplex 2 — one of the most common sexually transmitted diseases in the United States, according to a new report from the Centers for Disease Control and Prevention.

Although infection rates have not increased in recent years, health officials are concerned because individuals infected with genital herpes are at greater risk for infection with the virus that causes AIDS and for transmitting it to others.

Research shows that people with genital herpes are two to three times as likely to acquire H.I.V. as those without herpes, said Dr. John M. Douglas Jr., director of the agency’s division for preventing sexually transmitted diseases. “And herpes can also make H.I.V.-infected individuals more likely to transmit H.I.V. to others,” he added.

The latest figures, derived from the C.D.C.’s National Health and Nutrition Examination Survey for 2005-8, found striking disparities in infection rates, with women infected at almost twice the rate of men, and blacks three times as likely to be infected as whites. Black women have the highest rates of infection, with almost half infected. Biological factors and community trends are most likely responsible for the disparate infection rates, officials said.