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Friday, September 05, 2008
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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).
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