Section 3--Historical Trends in AIDS Incidence

A Closer Look at Changes in the Epidemic Over the Last Decade

Because of the impact of new combination therapies, researchers can no longer reliably predict the number of people who will be diagnosed with AIDS opportunistic infections each year (referred to in this document as AIDS incidence). There is no longer a way to determine the time it will take an infected individual on treatment to develop an opportunistic infection, because treatment has slowed the progression of disease for many individuals and the duration of the effects of these drugs are not certain. Moreover, after 1996, AIDS incidence will no longer provide an indication of trends in HIV transmission. We therefore present estimates of AIDS incidence from 1986 to 1996 to look at where the epidemic was heading nationally before the impact of new combination therapies.

While AIDS incidence remained highest among men who have sex with men (MSM), AIDS incidence increased most dramatically among women, African Americans, and people infected heterosexually and through injection drug use (IDU).

By gender * AIDS incidence increased among both men and women through 1994. In 1994, AIDS incidence began to drop slightly among men, with a more dramatic drop of 8% from 1995 to 1996. The decline in men is due to earlier declines in HIV infections among white gay men, in part, as a result of targeted prevention efforts. Among women, AIDS incidence was increasing at a rate of about 8% annually through 1994 before the impact of treatment. From 1995 to 1996, AIDS incidence among women increased 1%.

By race * AIDS incidence increased among all races through 1994, with the most significant increases seen among African Americans, who by 1996 accounted for more AIDS diagnoses annually than whites. In 1995, AIDS incidence dropped slightly among whites (-3%), with a more dramatic drop seen in 1996 (-13%) as treatment began having a greater effect. Among both African Americans and Hispanics, increases continued through 1995, with a decline in 1996 among Hispanics (-5%) and a leveling among African Americans (0%). Note: The percentage of cases among Asians and American Indians remains less than 1%.

By risk * AIDS incidence increased among all exposure groups through 1994, with incidence increasing most rapidly among heterosexuals. The first drop was seen among men who have sex with men (MSM) in 1995 (-2%), with a more significant drop in 1996 (-11%). AIDS incidence among injection drug users (IDU) was increasing at about 5% each year before treatment, and dropped 5% in 1996. AIDS incidence among heterosexuals was increasing by about 15% each year before 1996, and slowed to an increase of 7% in 1996, likely, in part, as a result of treatment.

By region of the United States * AIDS incidence increased in all regions through 1994, with the most dramatic increases in the South. In 1996, AIDS incidence dropped in the Midwest (-10%), the West (-12%),and the Northeast (-8%), and leveled in the South (0%).

By age * The greatest proportion of AIDS cases has always been among Americans ages 25-44. In 1996, an estimated 57,260 Americans were diagnosed with AIDS. Of these, almost 75% (42,460) were among people 25-44 years old, 21% were among Americans over the age of 44 (12,260), and less than 4% (2,040) were among people 13-24 years of age. The remainder were pediatric (less than age 13) AIDS cases.

Among children: Perinatal AIDS declines * Trends in AIDS incidence among children continued to demonstrate the dramatic success of efforts to reduce perinatal (mother-to-child) HIV transmission. In 1994, clinical trials showed that HIV-infected women could reduce the risk of transmitting the virus to their babies by as much as two-thirds through administration of zidovudine (ZDV or AZT) during pregnancy, labor, and delivery, and by giving their babies AZT for the first 6 weeks after birth. In 1994, the Public Health Service (PHS) issued guidelines for using AZT during pregnancy, and in 1995, published guidelines for routinely counseling all pregnant women about HIV and offering them an HIV test. As health care providers across the country incorporated these guidelines into clinical practice, perinatal AIDS incidence dropped dramatically. Between 1992 and 1996, the number of children with perinatally acquired AIDS dropped 43%. But despite declines in all racial/ethnic groups, the majority of perinatally acquired AIDS cases continue to occur among African-American and Hispanic children. This indicates the need for intensified efforts to prevent infection among minority women and to reach women who are infected with early prenatal care and preventive treatment.