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In most countries, reporting of acquired immunodeficiency syndrome (AIDS) cases has been incomplete and children are rarely included. Further, timely and appropriate use of antiretroviral therapy delays and may prevent the development of AIDS as previously defined. The advances in antiretroviral therapy (ART) therefore mean that public health surveillance of AIDS alone does not provide reliable population-based information on the scale and magnitude of the HIV epidemic. Data on adults and children diagnosed with HIV infection are more useful for determining populations needing prevention and treatment services. Simplified HIV case definitions are provided based on laboratory criteria combined with clinical or immunological criteria. The clinical staging of HIV-related disease for adults and children and the simplified immunological classification are harmonized to a universal four-stage system that includes simplified standardized descriptors of clinical staging events. The revised HIV case definitions and the clinical and immunological classification system proposed are intended for conducting public health surveillance and for use in clinical care services. WHO recommends that national programmes review and standardize their HIV and AIDS case reporting and case definitions in the light of these revisions.
In 1986, WHO developed a provisional clinical AIDS case definition for adults and children (Bangui definition) to report AIDS cases in resource-constrained settings. The definition was formalized in 1986 and modified in 1989 (for adults and adolescents only) to include serological HIV testing and then modified again in 1994 to accommodate 1993 revisions to European and United States Centers for Disease Control and Prevention definitions. European and United States Centers for Disease Control and Prevention definitions include specific case definitions for children. Studies in African settings suggest that the original WHO clinical case definitions for AIDS in children are not very sensitive or specific. AIDS case reporting in middle- and low-income countries has been incomplete and of variable accuracy, which has hampered its utility. Underreporting and delays in notification are frequent and exacerbated by weak heath information systems and the lack of diagnostic capacity. In highincome countries, AIDS case reporting combined with active AIDS case-finding has allowed AIDS notification and AIDS specific mortality to be monitored.