Sexually Transmitted Infections and HIV in the Southern United States: An Overview SEVGI O. ARAL, PHD, MSC, MA,* ANN O’LEARY, PHD,† AND CHARLENE BAKER, PHD‡ The geographic patterning of the HIV epidemic, as it evolves in the United States, has been remarkable in many ways. In the past 15 years, there has been a growth in the proportion of AIDS cases in blacks, in residents of the southeastern region, and in men and women infected through heterosexual contact. 1 Sexually transmit- ted diseases (STDs) other than HIV follow epidemiologic patterns similar to those of AIDS, 2 and syphilis and gonorrhea, like HIV, also disproportionately affect blacks in the nonurban south. 3 This special issue focuses on STDs and their determinants in the south- ern United States. In-depth looks at the epidemiology of specific sexually transmitted infections globally (and in the United States) suggest certain insights. First, populations are composed of many diverse subpopulations, and each population-level trajectory of an epidemic consists of many distinct subpopulation trajectories. 4,5 The trajectory of an epidemic of a specific STD differs in subpopulations depending on when and where the infection was introduced; the natural history and trans- missibility of the infection; the structure of sexual networks; the demographic, economic, social, and epidemiologic contexts; and the state of the health system. 6 Second, contextual factors such as demographic, economic, and social composition and trends are important determinants of epi- demic trajectory. The important effects of context on the trajectory of an epidemic often influence sexual networks, the health system, or cofactor effects that directly modify transmission efficiency. 7 Third, the temporal dimension plays an important role in STD epidemiology and prevention. 8 –11 STD epidemics evolve through sometimes predictable phases characterized by changing patterns in the distribution and transmission of STD-causing pathogens within and between subpopulations. Furthermore, STD-specific prevention and control programs also go through phases of devel- opment, implementation, scale-up, and maturation, and impact STD epidemiology. 12,13 Fourth, the structures of sexual links in a population—sexual networks and their evolution through time—are an important de- terminant of the spread of STD in populations. 6 It is within this framework that we approach the issue of high rates of HIV and STD prevalence in the southern United States. A review of 2 reportable sexually transmitted infections other than HIV suggests that (see Figs. 1 and 2): 1) regional differences in primary and secondary syphilis, which had been particularly marked among black men and women, have declined remarkably over the past decade. In fact, currently, the highest primary and secondary syphilis rates are observed in the West for white men; and 2) regional differences in gonorrhea rates have declined much less over the past decade. Regional differentials in gonorrhea rates are not marked among white men and women. Among black men and women, gonorrhea rates in the South have declined over the past decade, and the highest gonorrhea rates are reported in the Midwest. One measure of heterogeneity of STD morbidity in subpopula- tions is the disparity ratio, which depicts the ratio of black STD rates to white American STD rates. For the 2 STDs we have reviewed, the disparity ratio is actually higher in other regions than in the South, indicating that gonorrhea and syphilis rates among blacks are closer to rates among whites in the South than they are in the Midwest and Northeast (Figs. 3 and 4). Unlike the bacterial STD discussed here, viral STD cannot be cured (although they can be suppressed [herpes simplex virus]) and/or made less infectious [HIV]) through medication) and are more likely to persist in a particular geographic region. The HIV epidemic—whose emergence in the South may have been partly influenced by the high levels of bacterial STD, particularly syph- ilis, in the mid-1990s—is likely to endure and remain dispropor- tionately concentrated in the southern United States. This special issue focuses on STD in the southern United States and the societal determinants that influence STD rates. The articles in the issue address many topics that might be hypothesized to account for the differences in HIV/STD prevalence between the South and other regions of the country. There are remarkable sociodemographic differences between the southeastern United States and other parts of the country. The percentage of the population that is of African descent is considerably higher in the South than elsewhere. Blacks are disproportionately affected by STD, including HIV, independently of region of residence. Sec- ond, the deep South contains most of the most impoverished counties in the country. 14 For example, of the 229 counties with the highest poverty rates (more than 25%) in the country, 78% are in the South. Moreover, more people residing in the South live in nonurban areas. Of 229 poorest counties, 94% are rural. Fully 92% of rural blacks live in the South. In the remainder of this article, we review the 3 areas of sociodemographic difference outlined here The authors thank Emmet Swint, Patricia Jackson, and Melanie Ross for their outstanding support in the preparation of this article. Correspondence: Sevgi O. Aral, PhD, MSc, MA, Division of STD Prevention, Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Mailstop E-02, Atlanta, GA 30333. E-mail: SAral@cdc.gov From the *Division of STD Prevention, the †Division of HIV/AIDS Prevention-IRS, and the ‡Division of Violence Prevention, National Center for Injury Prevention and Control, Centers for Disease Control and Prevention, Atlanta, Georgia Sexually Transmitted Diseases, July supplement 2006, Vol. 33, No. 7, p.S1–S5 DOI: 10.1097/01.olq.0000223249.04456.76 Copyright © 2006, American Sexually Transmitted Diseases Association All rights reserved. S1