Update: trends in AIDS diagnosis and reporting under the expanded surveillance definition for adolescents and adults--United States, 1993.

The expansion of the surveillance case definition for acquired immunodeficiency syndrome (AIDS) in January 1993 (1) resulted in a large increase in reported AIDS cases. This increase has primarily reflected reports of human immunodeficiency virus (HIV)-infected persons in whom severe immunosuppression (CD4+ count < 200 T-lymphocytes/microL or a CD4+ T-lymphocyte percentage of total lymphocytes of < 14) had been diagnosed, which typically occurs before the onset of AIDS-defining opportunistic illnesses (AIDS-Ols, CDC clinical category C disease) (1,2). The inclusion of the CD4+ reporting criteria in AIDS surveillance has required an alteration in methods used to assess trends in AIDS incidence, previously based on the diagnosis of AIDS-Ols. This report first summarizes information about AIDS cases reported during 1993; then, to describe trends in AIDS incidence if the surveillance definition had not been expanded, this report uses estimates of eventual AIDS-Ol diagnosis dates for persons who were reported with AIDS based only on the CD4+ criteria.