The Centers for Disease Control and Prevention's announcement that nearly half of African-American women are infected with herpes has prompted reactions from panic and shock to outrage and disbelief. The study finds that women and blacks were most likely to be infected. The prevalence of herpes simplex virus 2 (HSV-2) was nearly twice as high among women (20.9 percent) than men (11.5 percent), and was more than three times higher among blacks (39.2 percent) than whites (12.3 percent). The most affected group was black women, with a prevalence rate of 48 percent.

The CDC collected the data as part of National Health and Nutrition Examination Survey culled from a two-part survey made up of a home interview and a health examination. The survey is designed to gather information not just about sexually transmitted diseases but on a broad range of health and nutrition issues of the U.S. household population. And the data carries a lot of weight. It has been used to influence policy like getting lead removed from gasoline and establishing national baseline estimates for cholesterol, blood pressure and Hepatitis C in the United States.

Based on the study, the higher rates of infection for African-American women are not due to increased risky behavior like having sex with drug users. However, where you live and whom you choose as sexual partners has a tremendous impact on your risk for STDs.

According to researchers, it's basically a numbers game. Women outnumber men in the general population, and the numbers are more sharply skewed among African Americans. We've all been bombarded with articles about the shortage of available black men and the high rate of black women (41 percent) who have never been married. This unbalanced dynamic can lead to people having multiple sexual partners, and in the United States, the frequency of overlapping relationships is higher among blacks than whites.

In addition to socioeconomic factors, women are at a greater risk simply because of anatomy. Genital tissue around the vagina is more susceptible to small tears during penetration making it easier to transmit STDs. The majority of infections might not occur just through women having sex with bisexual men but as likely via women transmitting it to heterosexual partners.

The fallout is that infection spreads through a sexual network faster. "A high prevalence of infection in the pool of potential partners can spread sexually transmitted infections rapidly within the ethnic group and keep it there," said Dr. Adaora A. Adimora, an infectious disease physician and associate professor at the University of North Carolina School of Medicine in Chapel Hill.