|
THE DEFINITION
OF AIDS
The term AIDS first appeared in the Morbidity and Mortality Weekly Report (MMWR) of the Centers for Disease Control (CDC) in 1982 to describe ". . . a disease, at least moderately predictive of a defect in cell-mediated immunity, occurring with no known cause for diminished resistance to that disease" (CDC, 1982b). The initial CDC list of AIDS-defining conditions, which included Kaposi's sarcoma (KS), Pneumocystis carinii pneumonia (PCP), Mycobacterium avium complex (MAC) and other conditions, has been updated on several occasions, with significant revisions (CDC, 1985a, 1987a, 1992a). For surveillance purposes, the CDC currently defines AIDS in an adult or adolescent age 13 years or older as the presence of one of 25 AIDS-indicator conditions, such as KS, PCP or disseminated MAC. In children younger than 13 years, the definition of AIDS is similar to that in adolescents and adults, except that lymphoid interstitial pneumonitis and recurrent bacterial infections are included in the list of AIDS-defining conditions (CDC, 1987b). The case definition in adults and adolescents was expanded in 1993 to include HIV infection in an individual with a CD4+ T cell count less than 200 cells per cubic millimeter (mm3) of blood (CDC, 1992a). The current surveillance definition replaced criteria published in 1987 that were based on clinical conditions and evidence of HIV infection but not on CD4+ T cell determinations (CDC, 1987a). In many developing countries, where diagnostic facilities may be minimal, epidemiologists employ a case definition based on the presence of various clinical symptoms associated with immune deficiency and the exclusion of other known causes of immunosuppression, such as cancer or malnutrition (Ryder and Mugewrwa, 1994a; Davachi, 1994). |