Epidemiology of HIV/AIDS --- United States, 1981--2005

In June 1981, the first cases of what was later called acquired immunodeficiency syndrome (AIDS) in the United States were reported in MMWR (1). Since 1981, the human immunodeficiency virus (HIV) epidemic has continued to expand in the United States; at the end of 2003, approximately 1,039,000--1,185,000 persons in the United States were living with HIV/AIDS, an estimated 24%--27% of whom were unaware of their infection (2). This report highlights several major epidemiologic features of the U.S. HIV epidemic, including the decrease in overall AIDS incidence, the substantial increase in survival after AIDS diagnosis (especially since highly active antiretroviral therapy [HAART] became the standard of care in 1996), and the continued disparities among racial/ethnic minority populations. These findings emphasize the need for a comprehensive national surveillance system, expanding the use of new HIV-testing technologies, promoting knowledge of HIV serostatus, and improving access to care and prevention interventions.

The analysis described in this report included 1) HIV/AIDS case reports (i.e., HIV infection with or without AIDS) from the 35 areas (33 states, Guam, and the U.S. Virgin Islands) with integrated, confidential, name-based HIV/AIDS surveillance of sufficient duration to produce reliable data (i.e., 2001--2004) and 2) AIDS case reports from the District of Columbia, the 50 states, and U.S. territories received by CDC through June 30, 2005. Cases of AIDS and HIV/AIDS were analyzed by year of earliest reported diagnosis of AIDS or HIV infection, respectively. Estimated case counts reflect adjustments made to annual numbers to account for case reporting delays and deaths. Cases without an assigned HIV-transmission category were redistributed based on historical trends in risk factors (3). For the analysis of trends and the impact of HAART on these trends, AIDS cases were divided into three cohorts on the basis of year of diagnosis: 1981--1995 (pre-HAART), 1996--2000 (early HAART), and 2001--2004 (HAART era). Survival analysis was conducted using the Kaplan-Meier method.

At the end of 2004, an estimated 1,147,697 HIV or AIDS cases had been diagnosed and reported to CDC (3). AIDS cases increased rapidly in the 1980s and peaked in 1992 (an estimated 78,000 cases diagnosed) before stabilizing in 1998; since then, approximately 40,000 AIDS cases have been diagnosed annually (3). Over the course of the epidemic, before this stabilization and during early prevention and treatment advances, the number of AIDS cases decreased 47% from 1992 to 1998, and decreases occurred in all demographic and transmission categories (4) (Table, Figure 1). The majority of AIDS cases continue to occur among males; however, the proportion of all AIDS cases increased from 15% (1981--1995) to 27% (2001--2004) for females (Table). Among age groups, the proportion of all AIDS cases decreased from 1.4% (1981--1995) to 0.2% (2001--2004) for persons aged <13 href="http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5521a2.htm?s_cid=mm5521a2_e#tab">Table).

Racial and ethnic minority populations have been disproportionately affected by the HIV epidemic. During 1981--1995, non-Hispanic whites were the predominant racial/ethnic group among persons who had AIDS diagnosed (47%); however, over time the proportion of cases among racial and ethnic minorities increased (2001--2004 cohort: non-Hispanic blacks accounted for 50%, and Hispanics accounted for 20%) (Table). Over time, all HIV-transmission categories demonstrated decreases in AIDS case numbers; however, the proportion of all AIDS cases for high-risk heterosexual contact (i.e., sexual contact with a person at high risk for or infected with HIV) during 1981--1995 was 10% and increased to 30% during 2001--2004 (Table).

During 2001--2004, an estimated 157,468 persons had HIV/AIDS diagnosed in the 35 areas reporting to CDC (Table), with the annual case number decreasing from 41,270 in 2001 to 38,730 in 2004. Fifty-one percent of HIV/AIDS cases diagnosed during 2001--2004 were among blacks. In 2004, estimated HIV/AIDS case rates for blacks (76.3 per 100,000 population) and Hispanics (29.5 per 100,000) were 8.5 and 3.3 times higher, respectively, than rates for whites (9.0 per 100,000) (3). Among males and females, case rates among blacks (males: 131.6 per 100,000; females: 67.0 per 100,000) were seven and 21 times higher, respectively, than rates for whites (males: 18.7 per 100,000; females: 3.2 per 100,000) (3). Among HIV/AIDS cases reported during 2001--2004, the most common route of HIV infection was attributed to male-to-male sexual contact (men who have sex with men [MSM]) (44%), followed by heterosexual contact (34%), injection-drug use (IDU) (17%), MSM/IDU (4%), and perinatal (0.6%) (Table). Although the HIV/AIDS case trend (2001--2004) for MSM was stable, the estimated annual percentage change for all other transmission categories indicated a substantial decrease, with the greatest decrease occurring for IDU (9.1%) (5).

During 1981--2004, a total of 522,723 deaths among persons with AIDS have been reported to CDC (Table). Substantial increases in survival after diagnosis of AIDS have been observed, particularly since 1996 (Figure 2). The proportion of persons living at 2 years after AIDS diagnosis was 44% for those with AIDS diagnosed from 1981--1992, 64% for 1993--1995, and 85% for 1996--2000. Survival for more than 1 year after diagnosis for persons with AIDS diagnosed during 1996--2003 was greater among Asians/Pacific Islanders, whites, and Hispanics, than among blacks and American Indians/Alaska Natives