AIDS cases are reported to CDC by all 50 states and the District of Columbia by use of a uniform case definition and case surveillance report form. This supplemental report includes cases reported according to the CDC guidelines for AIDS case surveillance and the case definition in effect at the time of their report.

Data in this report were compiled from cases reported to CDC through September 2002. Data on AIDS diagnoses, deaths among persons with AIDS, and persons living with AIDS were examined for 1994 to 2000. Data are statistically adjusted to correct for temporal delays in the reports of cases and deaths, and for unreported risk/exposure. Adjusted data are preferred for the assessment of trends since data by year of report are subject to surveillance artifacts such as variations in active surveillance.

Reporting delays (time between diagnosis of AIDS and report to CDC) may vary among exposure, geographic, racial/ethnic, age, and sex categories, and have been as long as several years for some AIDS cases. About 52% of all AIDS cases were reported to CDC within 3 months of diagnosis and about 88% were reported within 1 year. Among persons with AIDS, estimates in delay of reporting of deaths show that approximately 88% of deaths are reported within 1 year. Reporting delay adjustments to estimated AIDS data are calculated by a maximum likelihood statistical procedure, taking into account differences in reporting delays among exposure, geographic, racial/ethnic, age, sex, and vital status categories, but assuming that reporting delays within these groups have not changed over time (1, 2).

In 1998, the procedures for the investigation of cases reported without risk changed from ascertaining risk for all reported cases to ascertaining risk on high priority cases. As of September 2000, we began estimating risk distributions from statistical models and population-based samples. States continue to investigate any report of an unusual exposure to HIV and report these cases to CDC. CDC will continue to tabulate the number of documented unusual exposures to HIV as reported by the states.

Because recently reported AIDS cases are more likely to be reported without history of exposure to HIV through any of the categories listed in the hierarchy of exposure categories (NIR), recent AIDS diagnoses in some exposure categories will be underestimated unless an adjustment is made. For estimated AIDS diagnosis tables and estimated AIDS trends figures, the adjustment of NIR adult/adolescent cases is based on sex-, race-, and region-specific exposure category redistributions of cases diagnosed from 1990 through 1998 that were initially assigned to the NIR category but have subsequently been reclassified (1).

The rates for 1994 through 1999 were calculated using population denominators based on postcensus estimates from the U.S. Census Bureau. In the 2000 census as specified in the 1997 Office of Management and Budget (OMB) standards for the collection of race and ethnicity data, 31 race categories were used. The HIV and AIDS Reporting System continued to use the 4 race categories of non-Hispanic White, non-Hispanic Black, Asian/Pacific Islander, and American Indian/ Alaska Native in 2000. In order to produce rates by race, it was necessary to bridge the 2000 census population data for multiple races back to single race categories using proportional allocation at the county/ sex/single year of age level. In addition, the 2000 census data were modified to mirror the 1977 4 race categories where Asians, Native Hawaiians, and other Pacific Islanders were combined. The bridging procedure was created by the Statistics and Data Management Branch of the Division of HIV and AIDS Surveillance and Epidemiology, National Centers for Disease Control and Prevention.

References

1. Green TA. Using surveillance data to monitor trends in the AIDS epidemic. Statist Med 1998;17: 143-54
2. Karon JM, Devine OJ, and Morgan WM. Predicting AIDS incidence by estrapolating from recent trends. In Castillo-Chavez C, ed Mathematical and Statistical Approaches to AIDS Epidemiology (Lecture Notes in Biomathematics). Berlin: Springer-Verlag, 1989:58-88.