Forecasting the extent of the HIV/AIDS epidemic

Abstract This paper has a dual objective: (1) to describe the current status of the structure of a newly developed model system to generate a wide span of U.S. HIV/AIDS estimates; and (2) to implement that system through the development of a dataset of HIV/AIDS incidence and prevalence, by stage, in the U.S. for a range of past and future years. There are many uncertainties regarding the anticipated effects of HIV/AIDS; examination of many of these effects indicates multiple societal difficulties. The characteristic of AIDS-growth is that of a long-delayed but inexorable disabling morbidity “taking off” in 1991–1992 from an HIV population widely thought to be 1.0–1.5 million spread throughout the Nation. Although widely dispersed, its impact, even at this early stage of growth, is to endanger the health and social support systems of our urban centers. The spread of AIDS cases into the smaller cities and rural counties indicates that those problems will not be limited to our major cities. This paper provides new and purposely pessimistic estimates of the levels of prevalence and incidence of HIV/AIDS for future years, based on U.S. AIDS cases reported. Although these numbers are essentially upper bounds, their values are consistent with the upper sides of some recent broad band projections released in early Summer 1989 by the U.S. Government Accounting Office (GAO). However, our estimation has generated data within a more proscribed range. A first set of forecasts has been provided to the State of Virginia's Department of Health for their use in statewide resource planning. The United States and the world face a severe HIV pandemic in the coming decade. The certainty of the threat is acknowledged by all of the major private and public medical authorities and institutions. Yet, to date, no official projection of the emergence, the level, and the sweep of the epidemic has been accepted by the medical community. And, there is certainly little agreement on the impact on the delivery of health care services in the United States and Canada, as well as throughout the world. On 26 June 1989, the U.S. GAO released a report that concluded, in part, that the Federal government's official data [e.g. from the Centers for Disease Control's (CDC) Morbidity and Mortality Weekly Report (MMWR) of 12 May 1989] were greatly understating the epidemic's extent. Specifically, the CDC's estimate of 185,000–320,000 (cumulative) cases of AIDS expected to be reported by the end of 1991 contrasted with GAO's estimate of 300,000–480,000. An updated estimate by the CDC is 271,000 to 297,000 (source: MMWR , RR-16, 30 November 1990, p. 30, adjusted for underreporting). The statements below are derived from a Markov chain model of disease progression and a linear programming approach to backcalculation (using a body of data developed at George Mason University since 1987). The model estimates that cumulative cases of AIDS by end-1991 will be approximately 360,000 and, that by end-1992, those cases will have increased to approximately 473,000. The forecasts include corrections for reporting delays and are adjusted for an assumed CDC data-capture of 80%.