The Centers for Disease Control (CDC)
currently defines AIDS in an adult or adolescent age 13 years or
older as the presence of one of 26 conditions indicative of severe
immuno suppression associated with HIV infection, such as
Pneumocystis carinii pneumonia (PCP), a condition extraordinarily
rare in people without HIV infection. Most other AIDS-defining
conditions are also 'opportunistic infections' which rarely cause
harm in healthy individuals. A diagnosis of AIDS is also given to
HIV-infected individuals with a CD4+ T cell count less than 200
cells per cubic millimeter (mm3) of blood. 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.
The designation "AIDS" is a
surveillance tool. Surveillance definitions of AIDS have proven
useful epidemiologically to track and quantify the recent epidemic
of HIV-mediated immunosuppression and its manifestations. However,
AIDS represents only the end stage of a continuous, progressive
pathogenic process, beginning with primary infection with HIV,
continuing with a chronic phase that is usually asymptomatic, and
leading to progressively severe symptoms and, ultimately, profound
immunodeficiency and opportunistic infections and cancers.
