Backcalculation of the number with human immunodeficiency virus infection in the United States

The method of backcalculation was applied to national surveillance data on the acquired immunodeficiency syndrome (AIDS) in order to estimate the cumulative number of adults with human immunodeficiency virus type 1 (HIV-1) infection as of January 1, 1985 and July 1, 1987. A "plausible range" of estimates was constructed which reflected both uncertainty about the AIDS incubation distribution and random variation from selection and fitting of flexible models of the HIV-1 infection curve. The authors estimated that, as of 1985, 411,000 to 756,000 persons were infected. The infected population included 266,000 to 492,000 homosexual men, 69,000 to 136,000 intravenous drug users, 24,000 to 49,000 homosexual intravenous drug users, and 11,000 to 26,000 persons infected through heterosexual contact. The estimated prevalence of infection among persons aged 15-55 years was 0.31% in whites, 0.78% in Hispanics, and 0.81% in blacks. An estimated 32,000 to 66,000 women were infected. Compared with white women aged 15-55 years, the prevalence of infection was 5.3-fold higher in Hispanic women and 10.2-fold higher in black women. Plausible estimates for the total number infected by July 1987 ranged from 707,000 to 1,376,000, with the most likely estimate equal to 992,000. Backcalculation provides an assessment of the magnitude of the HIV-1 epidemic that is independent of estimates based on prevalence surveys in special populations. The estimates obtained from both methods are consistent and emphasize the need for vigorous programs to prevent the spread of HIV-1, especially in minority communities.