Objective: To measure the incidence and risk factors of AIDS-defining opportunistic illnesses (AOIs) in the pre-highly active antiretroviral therapy (HAART) (1993–1995), early-HAART (1996–2000), and late-HAART (2001–2008) periods.
Design: Prospective cohort analysis of AIDS surveillance data.
Methods: Individuals living with, or diagnosed with AIDS from 1993 through 2008 were included. Poisson regression models were used to estimate annual incidence rates of the eight most frequently occurring AOIs, and to compare these rates in the pre-HAART (1993–1995), early-HAART (1996–2000), and late-HAART (2001–2008) periods.
Results: There were 18 733 individuals with AIDS included; 5788 were diagnosed prior to 1993 and 12 945 were diagnosed between 1 January 1993 and 31 December 2008. The incidence rates of Pneumocystis jiroveci pneumonia, wasting syndrome, Kaposi's sarcoma, HIV encephalopathy, cytomegalovirus retinitis, cytomegalovirus, and esophageal candidiasis decreased during the study period, with the largest declines observed between the pre-HAART and early-HAART periods. Incidence rates also decreased between the early-HAART and late-HAART periods, though not as sharply. Incidence rate reductions between the earliest and latest period ranged from 84 to 99%.
Conclusions: Steep declines in incidence of AOIs were found following the introduction of HAART and continued into the late-HAART era. These declines reflect the impact of HIV diagnosis and treatment on a population level.